Flattened view for intra-lumenal navigation

ABSTRACT

Methods for creation and use (e.g., for navigation) of displays of flattened (e.g., curvature-straightened) 3-D reconstructions of tissue surfaces, optionally including reconstructions of the interior surfaces of hollow organs. In some embodiments, data comprising a 3-D representation of a tissue surface (for example an interior heart chamber surface) are subject to a geometrical transformation allowing the tissue surface to be presented substantially within a single view of a flattened reconstruction. In some embodiments, a catheter probe in use near the tissue surface is shown in positions that correspond to positions in 3-D space sufficiently to permit navigation; e.g., the probe is shown in flattened reconstruction views nearby view regions corresponding to regions it actually approaches. In some embodiments, automatic and/or easily triggered manual view switching between flattened reconstruction and source reconstruction views is implemented.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/650,973 filed on Mar. 26, 2020, which is a National Phase of PCTPatent Application No. PCT/EP2018/069569 having International FilingDate of Jul. 18, 2018, which claims the benefit of priority under 35 USC§ 119(e) of U.S. Provisional Patent Application Nos. 62/670,939 filed onMay 14, 2018 and 62/564,479 filed on Sep. 28, 2017, and also claimspriority of Great Britain Patent Application No. 1810992.6 filed on Jul.4, 2018.

PCT Patent Application No. PCT/EP2018/069569 is also aContinuation-in-Part (CIP) of PCT Patent Application No.PCT/IB2018/050201 having International Filing Date of Jan. 12, 2018,which claims the benefit of priority under 35 USC § 119(e) of U.S.Provisional Patent Application Nos. 62/564,479 filed on Sep. 28, 2017and 62/445,368 filed on Jan. 12, 2017.

The contents of the above applications are all incorporated by referenceas if fully set forth herein in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

Some embodiments of the present disclosure relate to the field ofmedical procedures using intrabody probes navigable within intrabodyspaces, and more particularly, to presentation of data acquired duringthe course of a catheter procedure.

Several medical procedures in cardiology and other medical fieldscomprise the use of catheters to reach tissue targeted for diagnosisand/or treatment while minimizing procedure invasiveness. Earlyimaging-based techniques (such as fluoroscopy) for navigation of thecatheter and monitoring of treatments continue to be refined, and arenow joined by techniques such as electromagnetic field-guided positionsensing systems. Refinements to techniques for registration ofpreviously imaged (for example, by CT and/or MRI) anatomical features ofa patient to electromagnetic field-sensed catheter position are asubject of ongoing research and development, for example as described inInternational Patent Application No. IB2016/052687 to Schwartz et al.filed May 11, 2016; and International Patent Application No.D32016/052692 to Schwartz et al. filed May 11, 2016. Intrabody sensingfrom catheter probes to determine information about, for example, tissuecontact and/or lesion assessment, has also been described (e.g.,International Patent Application No. PCT IB2016/052690 to Schwartz etal. filed May 11, 2016; and International Patent Application No.IB2016/052686 to Schwartz et al. filed May 11, 2016).

The present disclosure extends beyond the field of medical procedures oreven beyond the field of visualization of anatomical structures to thevisualization of a surface of bodies and objects in general.

SUMMARY OF THE INVENTION

A method of visualising a three-dimensional (3-D) model of athree-dimensional (3-D) surface, for example an inner surface, of a bodyis disclosed, The method comprises: obtaining the model, wherein themodel is defined by points on a model surface modelling the surface;defining a reference point within a volume surrounded by the modelsurface; applying an unfolding transformation to the points of the modelto transform each of the points to a corresponding point of an unfoldedmodel, wherein the transformation has the effect of transforming anotional closed surface, for example a sphere, centred on the referencepoint to a notional open surface such that for each point of the model,a normal distance between the notional closed surface and the point issubstantially equal to a normal distance between the notional opensurface and the corresponding point of the unfolded model; and causingdisplay of a view of the unfolded model.

In some embodiments, the body may be at least a portion of an internalorgan of an animal or human.

In some embodiments, the body may be a heart chamber.

In some embodiments, the method further comprises: receiving coordinatesfor the position of a catheter within the heart chamber; applying theunfolding transformation to the coordinates for the position of thecatheter within the heart chamber to obtain transformed coordinates forthe position of the catheter; and causing display of an indication ofthe catheter at the transformed coordinates together with the view ofthe unfolded model.

In some embodiments, the three-dimensional surface of the body may benon-developable.

In some embodiments, the view of the unfolded model may show at least80% of the points of the unfolded model.

In some embodiments, the view of the unfolded model may show all of thepoints of the unfolded model.

In some embodiments, the unfolding transformation comprises reducingazimuth and inclination angles about the reference point of each pointof the model and increasing the radial distance between each point ofthe model and the reference point, optionally such that a length betweentwo points of the model is preserved following the unfoldingtransformation

In some embodiments, the azimuth and inclination angles of each point ofthe models are defined with respect to a first line extending from thereference point and through a first surface reference point on thenotional closed surface, and a second line extending from the referencepoint and through a second surface reference point on the notionalclosed surface, and the unfolding transformation reduces the azimuth andinclination angles of each point of the model about the reference point.

In some embodiments, the unfolding transformation reduces the azimuthand inclination angle by multiplying each angle by a factor, wherein thefactor is positive and less than unity.

In some embodiments, the unfolding transformation comprises reducing theazimuth and/or the inclination angles of the point of the model. It willbe understood that “reducing” the azimuth and inclination anglescomprises reducing the absolute value of the angles. That is to say, ifan angle is defined as negative, the “reducing” comprises determiningthe absolute value of the angle, reducing the absolute value, and takingthe reduced angle to be the negative of the reduced absolute angle. Theresulting effect is to move all points angularly towards a lineextending from the reference point.

In some embodiments, the factor is set by a user to control a degree ofunfolding, wherein a maximum degree of unfolding signifies azero-curvature notional open surface.

In some embodiments, the reducing comprises multiplying the azimuthand/or inclination angle by an unfolding factor 0<α<1. The azimuth anglemay be multiplied by a first unfolding factor α₁, and the inclinationangle may be multiplied by a second unfolding factor α₂ different fromthe first unfolding factor. The first unfolding factor and secondunfolding factor may be the same.

In some embodiments, the first and/or second surface reference pointsmay be determined by a user.

In some embodiments, increasing the radial distance between each pointof the model and the reference point comprises adding a multiplicativeproduct of a value indicative of the size of the notional closedsurface; and the difference between the inverse of the factor and unity.

In some embodiments, the notional closed surface may be at leastpartially within the model surface.

In some embodiments, the notional closed surface may be entirely withinthe model surface.

In some embodiments, the notional open surface may be a portion of asphere centred on the reference point.

In some embodiments, the notional open surface may have a non-zerocurvature.

In some embodiments, the notional open surface may have zero curvature.

In some embodiments, obtaining the model comprises obtaining arepresentation of the points of the model in polar coordinates, andapplying a transformation comprises: transforming the azimuthal andinclination coordinates using a Mollweide cartographic projectiontransformation; multiplying the transformed azimuthal and inclinationcoordinates by the factor;

and transforming the resulting multiplied transformed coordinates usingthe inverse of the Mollweide cartographic projection transformation. Insome embodiments, obtaining the model comprises obtaining arepresentation of the points of the model in polar coordinates, and thetransformation comprises a cartographic projection onto the notionalopen surface of the azimuthal and inclination coordinates of each pointof the model to respective first and second cartesian coordinates of thecorresponding point of the unfolded model.

Obtaining a representation of the points of the model in polarcoordinates may comprise transforming the coordinates of the points ofthe model into polar coordinates using conventional transformations topolar coordinates.

In some embodiments, the transformation further comprises defining thethird cartesian coordinate of the corresponding point of the unfolded asthe sum of the radial coordinate of the point of the model and a thirdcartesian coordinate on the notional open surface corresponding to thefirst and second cartesian coordinates of the corresponding point of theunfolded model. In some embodiments, the cartographic projection may bea Plate Carrée projection.

In some embodiments, the cartographic projection may be a Mollweideprojection.

In some embodiments, the method further comprises causing the displayingof an icon indicative of the direction at which the portion of theinternal organ is viewed with respect to the animal or human.

In some embodiments, the method further comprises receiving, via a userinterface, an indication of a first orientation of the unfolded modeland causing display of the view of the unfolded model at the firstorientation indicated via the user interface.

In some embodiments, the method further comprises causing display of asecond view of the unfolded model.

In some embodiments, the second view may have a viewing direction thatis opposite of the viewing direction of the first view.

In some embodiments, the second view may have a viewing direction thatis perpendicular to the viewing direction of the first view.

In some embodiments, the method further comprises receiving, via userinterface, an indication of a second orientation of the unfolded model,and causing the display, for example so that both views are displayedfor an overlapping time period or so that one view after the other withonly one view displayed at the same time, of the second view of theunfolded model at the second orientation indicated via the userinterface.

In some embodiments, the view of the unfolded model comprisesinformation pertaining to the current state of a time varyinginformation.

In some embodiments, the time varying information may be different atrear and front portions of the heart chamber.

In some embodiments, the time varying information may be an electricalactivation map.

In some embodiments, the time varying information may be an edema map

In some embodiments, the method comprises causing simultaneous displayof a plurality of views of the unfolded model at a plurality ofdifferent orientations.

In some embodiments, causing the display comprises causing a pluralityof views of the unfolded model at a plurality of different orientations,wherein each view of the plurality of views is displayed sequentially.In other words, is view of the plurality of views is displayed one-afterthe other so as to provide the effect of continuous movement of the viewof the unfolded model.

In some embodiments, the method further comprises causing simultaneousdisplay of a plurality of views of the unfolded model, wherein each viewis indicative of a different degree of unfolding.

In some embodiments, the points of the model may be obtained frommeasurements taken inside the body.

In some embodiments, the measurements may have been taken by a catheterinside the body.

In some embodiments, the method further comprises: obtaining additionalpoints of the model; computing an updated unfolded model by applying thetransformation to the additional points to transform each of theadditional points of the model to a corresponding additional point ofthe unfolded model; and causing display of a view of the updatedunfolded model, wherein the updated unfolded model comprises theadditional points of the unfolded model.

In some embodiments, the view of the unfolded model is a predefinedview, wherein the predefined view is displayed in accordance with atleast one of a plurality of predefined viewing parameters, the pluralityof predefined viewing parameters comprising: the factor; the valueindicative of the size of notional closed surface; the first and/orsecond surface reference point on the notional closed surface; theorientation of the view of the unfolded surface.

In some embodiments, the method further comprises displaying theunfolded model as a combination of a central model modelling a portionof the surface of the heart chamber in a first rendering method, and aperipheral model modelling the rest of the heart chamber in a secondrendering method, wherein the peripheral model is spread at theperiphery of the central model.

In some embodiments, the method further comprises defining the firstportion of the surface of the heart chamber as a portion of the surfacelying at one side of a cutting surface and the rest of the surface ofthe heart chamber as that portion of the surface lying at the other sideof the cutting surface, wherein the cutting surface is defined as asurface going through a desired vantage point and perpendicularly to adesired viewing direction.

There is further provided a method of presenting a three-dimensionalmodel of an surface of heart chamber wall, the method comprising:determining a viewing point and a viewing direction; unfolding the modelso that portions of the surface that are behind a cutting surface goingthrough the vantage point perpendicularly to the viewing direction arepresented peripherally to portions of the surface that are in front thecutting surface; and displaying the unfolded model together with an iconrepresenting the viewing direction.

There is further provided an apparatus for displaying a model using amethod in accordance with some methods, the apparatus comprising a userinterface configured to allow a user to indicate a desired vantage pointand a desired viewing direction.

In some embodiments, the apparatus further comprises a display showingthe orientation of the viewing direction near the resulting unfoldedthree-dimensional model.

In some embodiments, the user interface allows the user to indicatedifferent vantage points and/or viewing angle continuously, and thedisplay shows the unfolded model changing simultaneously with thevantage point and/or viewing angle.

There is also disclosed an apparatus comprising: an input moduleconfigured to receive signals from a catheter, wherein the signals areindicative of measurements taken by the catheter inside a heart chamber;a converting module for converting the signals into coordinates ofpoints defining a model surface modelling a three-dimensional model of athree-dimensional surface of the heart chamber, and coordinates for theposition of the catheter within the heart chamber; a processorconfigured to apply a transformation to the points of the model totransform each of the points to a corresponding point of an unfoldedmodel; and a display for displaying a view of the unfolded model.

In some embodiments, the processor may be configured to carry outmethods in accordance with some embodiments of the present disclosure.

In some embodiments, the apparatus may further comprise a user interfaceconfigured to receive display instructions from a user, wherein theapparatus is configured to display a view of the unfolded model inaccordance with the display instructions.

In some embodiments, the measurements taken inside the heart chamber maybe electrical measurements.

In some embodiments, the measurements taken inside the heart chamber maybe magnetic measurements.

In some embodiments, the apparatus may be configured to display an iconindicative the direction at which the unfolded model is viewed withrespect to a human body.

In some embodiments, the display instructions comprise the orientationof the view of the unfolded model.

In some embodiments, the apparatus may be configured to display a secondview of the unfolded model.

In some embodiments, the display instructions may comprise theorientation of the second view of the unfolded model.

In some embodiments, the apparatus may be configured to displayinformation pertaining to time varying information.

In some embodiments, the apparatus may be configured to simultaneouslydisplay a plurality of views of the unfolded model at a plurality ofdifferent orientations.

In some embodiments, the apparatus is configured to display a pluralityof views of the unfolded model at a plurality of different orientations,wherein each view of the plurality of views is displayed sequentially.

In some embodiments, the apparatus may be configured to simultaneouslydisplay a plurality of views of the unfolded model, wherein each view isindicative of a different degree of unfolding.

There is also disclosed a system comprising: a catheter configured totake measurements inside a heart chamber; an input module configured toreceive signals from the catheter, wherein the signals are indicative ofthe measurements a converting module for converting the signals intocoordinates of points defining a model surface modelling athree-dimensional model of a three-dimensional surface of the heartchamber and coordinates for the position of the catheter within theheart chamber; a processor configured to compute an unfolded model byapplying a transformation to the points of the model to transform eachof the points to a corresponding point of an unfolded model; and adisplay for displaying a view of the unfolded model.

Further disclosed is a method of visualising a catheter within athree-dimensional model of a three-dimensional surface of a heart atriumwith a catheter in the atrium, the method comprising: obtaining themodel, wherein the model is defined by points on a model surfacemodelling the surface, and wherein the model comprises catheter pointsdefining a position of a distal end of the catheter inside the modelsurface; applying an unfolding transformation to points of the model,including the catheter points, to transform each of the points to acorresponding point of an unfolded model; and causing display of a viewof the unfolded model, wherein the view of the unfolded model includes amarking at the transformed catheter points, the marking being indicativeof the position of the distal end of the catheter.

In some embodiments, the method further comprises: obtaining newcatheter points defining a new position of the distal end of thecatheter inside the model surface; applying the unfolding transformationto the new catheter points; and causing display of a view of theunfolded model, wherein the marking is moved to be at the transformednew catheter points, the marking being indicative of the new position ofthe distal end of the catheter. In some embodiments, moving the markingmay comprise making it disappear from the old place and appear in thenew place.

Further disclosed is a method of assisting a doctor in guidingnavigation of a catheter probe inside a heart chamber, the methodcomprising: obtaining an unfolded three dimensional (3-D) model of theheart chamber with the catheter probe therein, optionally, the unfolded3-D model having a front surface, facing the model inside of the heartchamber, and a back surface, facing away from the model inside of theheart chamber; generating a first view of the model, the first viewshowing the model from a first direction; generating a second view ofthe model, the second view showing the model from a second directiondifferent from the first direction; and providing the first and secondviews for simultaneous display.

In some embodiments, the method comprises providing the views comprisesproviding the two views simultaneously to a single display panel.

In some embodiments, the method comprises providing the views comprisesproviding the two views simultaneously for side by side display.

In some embodiments, the method comprises the first and seconddirections are perpendicular to each other.

In some embodiments, obtaining the unfolded model comprises: obtaining afolded 3-D model of the heart chamber, and unfolding the folded 3-Dmodel of the heart chamber.

In some embodiments, obtaining of the unfolded 3-D model of the heartchamber comprises: receiving electrical measurements from the catheterprobe; and generating the unfolded three-dimensional (3-D) model of theheart chamber based on the electrical measurements received from thecatheter probe.

In some embodiments, the method further comprises: generating a thirdview, showing a partly unfolded 3-D model of the heart chamber, andproviding the third view for display for time periods overlapping withtime periods during which the first and second views are displayed.

There is further provided an apparatus for assisting a doctor in guidingnavigation of a catheter probe inside a heart chamber, the apparatuscomprising a processor configured to: obtain an unfolded threedimensional (3-D) model of the heart chamber with the catheter probetherein, facing away from the modeled inside of the heart chamber;generate a first view of the model, the first view showing the modelfrom a first direction; generate a second view of the model, the secondview showing the model from a first direction; provide the first andsecond views for simultaneous display.

In some embodiments, the processor is configured to provide the firstand second views simultaneously to a single display panel.

In some embodiments, the processor is configured to provide the viewssimultaneously for side by side display.

In some embodiments, the processor is configured to obtain the unfoldedmodel by: obtaining a folded 3-D model of the heart chamber, andunfolding the folded 3-D model of the heart chamber.

In some embodiments the processor is configured to obtain the unfolded3-D model of the heart chamber by: receiving electrical measurementsfrom the catheter probe; and generating the unfolded three-dimensional(3-D) model of the heart chamber based on the electrical measurementsreceived from the catheter probe.

In some embodiments, the apparatus further comprises a displayconfigured to receive the views from the at least one processor anddisplay them simultaneously side by side.

In some embodiments, the apparatus further comprises a catheter probe.

In some embodiments, the catheter probe includes a plurality ofelectrodes configured to communicate with the at least one processor.

In some embodiment, the at least one processor is further configured togenerate a third view, showing a partly unfolded 3-D model of the heartchamber, and providing the third view for display for time periodsoverlapping with time periods during which the first and second view aredisplayed.

There is further provided a display panel, displaying a partly unfoldedview of a 3-D model of a heart chamber.

There is further provided an apparatus comprising a processor configuredto obtain a folded 3-D model of a heart chamber, and partially unfoldthe obtained folded 3-D model. In some embodiments, the processor isconfigured to obtain the folded 3-D model of the heart chamber byreceiving electrical measurements from a catheter probe within the heartchamber, and generating the folded 3-D model based on the electricalmeasurements.

In some embodiments, the apparatus further comprises a user interfaceallowing a user to indicate a degree of unfolding, and the processor isconfigured to partially unfold the obtained folded 3-D model to thedegree indicated via the user interface.

In some embodiments, the user interface includes an adjustable inputelement, and when a user adjusts a position of the input element, thefolded model is unfolded to a degree depending on the position of theinput element. In some such embodiments, the input element may be anon-screen input element.

Also disclosed is a method of displaying relief details distributedacross a curved surface, the method comprising: re-distributing therelief details on the curved surface so that the surface is divided toan occupied portion occupied with relief details and a free portion freefrom relief details; increasing the curvature of the curved surface; anddisplaying the occupied portion of the increased-curvature curvedsurface.

In some embodiments, notional lines, each connecting a position of arelief detail before the re-distribution to a position of the reliefdetail after the re-distribution, don't intersect.

In some embodiment, the curved surface is non-developable.

In some embodiments, the surface area of the occupied portion after thecurvature increase is between half and twice the surface area of theentire surface before the curvature increase.

In some embodiments, the curved surface is a model of a surface of abody potion.

There is also provided a method of assisting a physician in carrying outa catheterization process, the method comprising: receiving data from acatheter; generating, based on the data received from the catheter, a3-D model of a curved surface of a body part, the model comprisingrelief details distributed across the curved surface; re-distributingthe relief details on the curved surface so that the surface is dividedto an occupied portion occupied with relief details and a free portionfree from relief details; increasing the curvature of the curvedsurface; and displaying to the physician, during the catheterizationprocess, the occupied portion of the increased-curvature curved surface.

As will be appreciated by one skilled in the art, embodiments disclosedherein may be used to visualize a three-dimensional model of an innerthree-dimensional surface of any type of body. For example, the body maybe any type of internal organ of an animal or human or of any type ofbody lumen (e.g. a heart chamber, a blood vessel, a lymph vessel, abone, membrane, cyst, gastrointestinal tract portion, kidney/urinarytract portion, respiratory tract portion, reproductive tract portion,eye, ear, CNS ventricle, peritoneum, and/or another natural and/orartificial space such as implant surroundings). In embodiments disclosedherein, a heart chamber is used as an example of a particular body towhich such a visualization method is optionally applied. However, itshould be understood that the technique optionally applies, changed asnecessary, to the inner three-dimensional surface of any body or portionthereof. In some embodiments, a representation of an organ exteriorsurface (e.g., of a heart, liver, kidney, brain, and/or portion(s)thereof such as a right atrium) is flattened.

Unless otherwise defined, all technical and/or scientific terms usedherein have the same meaning as commonly understood by one of ordinaryskill in the art to which the present disclosure pertains. Althoughmethods and materials similar or equivalent to those described hereincan be used in the practice or testing of embodiments, exemplary methodsand/or materials are described below. In case of conflict, the patentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and are notintended to be necessarily limiting.

As will be appreciated by one skilled in the art, aspects of the presentdisclosure may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present disclosure may take theform of an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system”(e.g., a method may be implemented using “computer circuitry”).Furthermore, some embodiments of the present disclosure may take theform of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon. Implementation of the method and/or system of some embodimentsof the disclosure can involve performing and/or completing selectedtasks manually, automatically, or a combination thereof. Moreover,according to actual instrumentation and equipment of some embodiments ofthe method and/or system, several selected tasks could be implemented byhardware, by software or by firmware and/or by a combination thereof,e.g., using an operating system.

For example, hardware for performing selected tasks according to someembodiments could be implemented as a chip or a circuit. As software,selected tasks according to some embodiments could be implemented as aplurality of software instructions being executed by a computer usingany suitable operating system. In an exemplary embodiment, one or moretasks according to some exemplary embodiments of method and/or system asdescribed herein are performed by a data processor, such as a computingplatform for executing a plurality of instructions. Optionally, the dataprocessor includes a volatile memory for storing instructions and/ordata and/or a non-volatile storage, for example, a magnetic hard-diskand/or removable media, for storing instructions and/or data.Optionally, a network connection is provided as well. A display and/or auser input device such as a keyboard or mouse are optionally provided aswell. Any of these implementations are referred to herein more generallyas instances of computer circuitry.

Any combination of one or more computer readable medium(s) may beutilized for some embodiments. The computer readable medium may be acomputer readable signal medium or a computer readable storage medium. Acomputer readable storage medium may be, for example, but not limitedto, an electronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, or device, or any suitable combinationof the foregoing. More specific examples (a non-exhaustive list) of thecomputer readable storage medium would include the following: anelectrical connection having one or more wires, a portable computerdiskette, a hard disk, a random access memory (RAM), a read-only memory(ROM), an erasable programmable read-only memory (EPROM or Flashmemory), an optical fiber, a portable compact disc read-only memory(CD-ROM), an optical storage device, a magnetic storage device, or anysuitable combination of the foregoing. In the context of this document,a computer readable storage medium may be any tangible medium that cancontain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium and/or data usedthereby may be transmitted using any appropriate medium, including butnot limited to wireless, wireline, optical fiber cable, RF, etc., or anysuitable combination of the foregoing.

Computer program code for carrying out operations for some embodimentsmay be written in any combination of one or more programming languages,including an object-oriented programming language such as Java,Smalltalk, C++ or the like and conventional procedural programminglanguages, such as the “C” programming language or similar programminglanguages. The program code may execute entirely on the user's computer,partly on the user's computer, as a stand-alone software package, partlyon the user's computer and partly on a remote computer or entirely onthe remote computer or server. In the latter scenario, the remotecomputer may be connected to the user's computer through any type ofnetwork, including a local area network (LAN) or a wide area network(WAN), or the connection may be made to an external computer (forexample, through the Internet using an Internet Service Provider).

Some embodiments may be described below with reference to flowchartillustrations and/or block diagrams of methods, apparatus (systems) andcomputer program products according to embodiments. It will beunderstood that each block of the flowchart illustrations and/or blockdiagrams, and combinations of blocks in the flowchart illustrationsand/or block diagrams, can be implemented by computer programinstructions. These computer program instructions may be provided to aprocessor of a general-purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments are herein described, by way of example only, withreference to the accompanying drawings. With specific reference now tothe drawings in detail, it is stressed that the particulars shown are byway of example, and for purposes of illustrative discussion ofembodiments. For example, although visualization of inner surfaces isdescribed below, the disclosure is equally applicable to other surfaces,for example outer surfaces of a body. In this regard, the descriptiontaken with the drawings makes apparent to those skilled in the art howembodiments may be practiced.

In the drawings:

FIG. 1A schematically represents anatomical features of a left atriumrepresented in its usual 3-D shape, according to some embodiments of thepresent disclosure.

FIG. 1B schematically represents anatomical features of a left atriumspread out into a flattened shape, according to some embodiments of thepresent disclosure;

FIG. 1C shows a reconstruction of a left atrium inner lumenal surfacerepresented in its usual (un-flattened) 3-D representation, according tosome embodiments of the present disclosure;

FIG. 1D is a view of a flattened representation of the sourcereconstruction of FIG. 1C, according to some embodiments of the presentdisclosure;

FIG. 1E is a flowchart outlining a method of producing an image of aflattened representation, according to some embodiments of the presentdisclosure;

FIG. 1F is a flowchart outlining a method of producing a flattenedrepresentation, according to some embodiments of the present disclosure;

FIG. 1G is a flowchart outlining a method of determining an orientationof a representation of a curved body organ surface, according to someembodiments of the present disclosure;

FIG. 2A shows a flattened representation view of left atrium anatomy,according to some embodiments of the present disclosure;

FIG. 2B shows the view of FIG. 2A, with additional markers indicatingablation points and catheter probe, according to some embodiments of thepresent disclosure;

FIG. 3 schematically represents a flattened representation of leftatrium anatomy including a superimposed activation map, according tosome embodiments of the present disclosure;

FIG. 4 schematically represents a navigational situation of a catheterprobe represented as moving with respect to a flattened representationview of a left atrium, according to some embodiments of the presentdisclosure;

FIGS. 5A-5B schematically represent indications of navigational target,distance from a surface and/or direction of a catheter probe moving withrespect to a flattened reconstruction view, according to someembodiments of the present disclosure;

FIGS. 6A-6B show the views of FIGS. 1C-1D, respectively, together withinindications of the position of a catheter probe.

FIGS. 7A-7B show the same flattened representation shown in FIGS. 1D and6B, viewed at different tilt angles, according to some embodiments ofthe present disclosure;

FIGS. 8A-8B illustrate a non-flattened and flattened representations ofa left atrium having a contour overlay, according to some embodiments ofthe present disclosure;

FIG. 9A shows a planar sectioning of a 3-D representation of a body partreconstruction, according to some embodiments of the present disclosure;

FIGS. 9B-9C show views looking into the two sectioned parts of body partreconstruction, according to some embodiments of the present disclosure;

FIGS. 10A-10D show a range of standard camera-type views of the interiorof a reconstructed left atrium, according to some embodiments of thepresent disclosure;

FIGS. 11A-11D show different flattened representations of right atria,according to some embodiments of the present disclosure;

FIG. 12 presents a detailed flattened representation of a left atriumbased on data acquired using field gradient-based remote imaging,according to some embodiments of the present disclosure;

FIG. 13 schematically represents a system for production of a flattenedrepresentation, according to some embodiments of the present disclosure;

FIGS. 14A-14E schematically illustrate different 3-D examples ofpre-flattening and post-flattening global curvatures and relief details,according to some embodiments of the present disclosure.

FIGS. 15A-15D schematically illustrate features visible on a flattenedrepresentation view of a right atrium (FIGS. 15A-15B) and left atrium(FIGS. 15C-15D), according to some embodiments of the presentdisclosure;

FIG. 16A illustrates a triangular meshing of the shape of a left atrium,according to some embodiments of the present disclosure;

FIGS. 16B-16E illustrate different flattenings of the triangular meshingof FIG. 16A, according to some embodiments of the present disclosure;and

FIGS. 17A-17B each show a sequence of flattened 3-D images produced fromearlier-measurement phase maps, and later-measurement phase, morerefined maps of body lumen wall structure, based on a cumulative set ofintralumenal voltage measurements, according to some embodiments of thepresent disclosure.

FIG. 18 illustrates a method of visualizing a 3-D model of an inner 3-Dsurface of a body.

FIG. 19 illustrates an implementation of an apparatus configured toperform any one of the methodologies discussed herein.

FIG. 20 illustrates an unfolding transformation method for use invisualizing a 3-D model of an inner 3-D surface.

FIG. 21 illustrates a block diagram of an unfolding transformationmethod for use in visualizing a 3-D model of an inner 3-D surface.

FIGS. 22A-22C illustrate an example of the unfolding transformationillustrated in FIG. 20 for points of the model defined in polarcoordinates.

FIG. 23 illustrates an example display of a viewing arrangement of anunfolded model of a heart chamber in accordance with some embodiments ofthe invention.

FIGS. 24A to 24E show an unfolded model of a heart chamber at fivedifferent degrees of unfolding.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

Some embodiments of the present disclosure relate to the field ofmedical procedures using intrabody probes navigable within intrabodyspaces, and more particularly, to presentation of data acquired duringthe course of a catheter procedure.

Overview

An aspect of some embodiments of the present disclosure relates tomethods and system for the displaying of flattened representations oftissue surfaces; and in particular embodiments, displays of flattenedrepresentations of the interior surfaces of hollow organs (bodycavities). Surfaces are optionally presented from one or both of theirtwo sides: e.g., a represented interior surface of a hollow organ may bepresented for viewing from an external side or an internal side of thesurface (also referred to herein as “epicardial” and “endocardial”views, respectively). From some viewing angles, a portion of an externalview of the internal surface may be viewed along with a portion of aninternal view of the internal surface. In some embodiments, exteriortissue surfaces are represented.

In some embodiments, data comprising a 3-D representation (that is, arepresentation having width, length, and depth) of a curved body tissuesurface (e.g., a surface of a body organ or portion thereof) are subjectto a geometrical transformation which results in a differentrepresentation, which is also 3-D (having width, length and depth), butis potentially better suited to display of the organ surface andoptionally a volume defined thereby, substantially within a single view.Herein, the result obtained by such a transformation is referred to as a“flattened reconstruction”. A “reconstruction”, “3-D representation” or“3-D model” of a shape, as the terms are used interchangeably herein,comprises a data structure stored in computer memory specifying 3-Dcoordinates of positions defining a surface of the shape.

Moreover, the reconstruction (3-D representation, 3-D model) may be“flattened”. This is also referred to herein as“curvature-straightened”, “relatively straightened”, and “unrolled”.Also herein, “reduction” of curvature refers to making a curvaturerelatively straighter and/or more gradual. In the case of flattened 3-Dmodels, the flattening is in the sense that a surface of the first (or“source”) 3-D representation which curves to extend around somereference point and/or path is converted (in the second/modified or“flattened” 3-D representation) to a relatively straightened surface.The transformation is performed so that while a global curvature isrelatively straightened (reduced) by the flattening, relief detailsdistributed along the curved surface are retained. Moreover, in someembodiments, the flattening is done so that other positions in thevolume of the source 3-D model away from the surface are alsotransformed, and have corresponding positions within the flattened 3-Drepresentation. In some embodiments, the transformation is 1:1, so thatpositions in the flattened 3-D model uniquely correspond to positions inthe source 3-D model. This may be contrasted, for example, with a 2-Dimage projected from a source 3-D model, which collapses representationthrough a range of positions in depth to a single pixel or other 2-Dimage region. The flattened 3-D model may, however, be converted in turnto an image, such as a 2-D image for viewing. A potential advantage ofthe intermediate flattened 3-D model, over direct projection of a source3-D model to an image, is in allowing the surface to be presented insubstantially its entirety, while its features retain properties underchanges in viewing perspective (e.g., changes of a virtual camera'svantage point) that correspond to how objects normally behave in thevisual field of an observer. This may assist a person viewing thechanging image to maintain a sense of feature persistence. For example,changes in foreshortening, size, and/or mutual masking behave much asany normal object in the ordinary visual field behaves, so that therelationship among various parts of the flattened 3-D model remainsvisually clear. In contrast, changing the viewing perspective of afisheye lens type view (e.g., a view that projects 2 n steradians ormore of solid angle view onto a 2-D image) results in patterns ofchanging distortion (radial compression as features come near the imagerim, in particular) which are potentially more disorienting. This mayinterfere with recognition of features, and/or recognition of featuresas being the same feature, as the viewing perspective changes. In someembodiments, images generated from the flattened 3-D model are used inreal-time applications, e.g., visualization of the navigation of a probewithin the modeled space by the placing of an indication at a positionwithin the flattened 3-D model which converts, when an image is madefrom the flattened 3-D mode, to an indication of the probe positionrelative to other features in the flattened 3-D model. In bettermatching the normal behavior of visual objects, the images maypotentially help a user to maintain a sense of orientation in the spacebeing navigated.

Optionally, the global curvature targeted for straightening by theflattening is defined by a function such as a sphere, ellipsoid,parametric curve (e.g., Bézier curve), combination of sphericalharmonics, and/or long wavelength frequency domain components of aFourier transform of the surface transformed back into the spatialdomain. A surface defined by such a function is also referred to hereinas a “surface of global curvature”. In some embodiment, the globalcurvature is at least partially implicit in the choices of coordinatesystems used during flattening; for example, in some embodiments, aspherical global curvature is implicit in the choice of a transform thatcomprises conversion of coordinate values in a spherical coordinatesystem directly into coordinate values of a Cartesian coordinate system.Herein, the flattening transformation is also referred to as“unwrapping”. The term arises in the sense that a surface which curvesaround some central region in a source 3-D model “wraps around” thatcentral region; and when the flattened 3-D model is created, the samesurface is effectively flattened so that the central region is no longerenclosed by it. It should be understood, however, that other regions inthe volume of the source 3-D model away from the unwrapped surface arealso transformed by the “unwrapping” in some embodiments.

The relief details comprise, e.g., details having distances from thereference point which vary separately from the surface of globalcurvature. For example, depths of the relief details may add linearly todepths of the global curvature in spherical coordinates or in anothercoordinate system. The selection of a global curvature for production ofthe flattened reconstruction (and/or selection of a method of modelingglobal curvature) is optionally influenced by the structure ofreconstruction details (the relief details) which are to be preserved orsuppressed: for example, scale and/or shape. Insofar as the globalcurvature follows the shape of some detail in the source reconstruction,that detail will tend to be suppressed in the flattened reconstruction.

The relief details which are represented by their depth in the flattenedreconstruction and/or a view thereof are optionally distorted (at leastin some places) by some amount in the dimensions of width, length,and/or depth; for example as a by-product of the transformation used toproduce the flattened reconstruction. In some embodiments, width andlength in the flattened reconstruction correspond to spherical anglepositions in the source reconstruction.

Optionally (e.g., when the source reconstruction substantially surroundsthe reference point), the flattening comprises introducing one or morediscontinuities, for example “cuts” in the flattened reconstructioncompared to the source reconstruction. Optionally, discontinuities aresuppressed in the flattened reconstruction and/or a view thereof byduplication, for example, by concatenation of data from another portionof the reconstruction (optionally with reflection or anothermanipulation) at the edges of discontinuities. Additionally oralternatively, insofar as the flattened reconstruction itself per se is(and/or is part of) a data structure in computer memory, it is notnecessarily bound by the limitations of 3-D space. In particular, thereis no necessarily inherent contradiction in the flattened reconstructionbeing represented in memory as both flattened and circumferentiallycontinuous in all directions (e.g., structured as one or more circularlinked lists, giving the data structure spherical, toroidal, infiniteplanar, or another type of logically continuous topology). However, atsome stage during preparation of a viewable image, at least onediscontinuity will generally be introduced so that the image itself canbe flat, or at least contained within a limited viewing angle (incontrast, for example, to an immersive and 360-degree, 4π steradianssurrounding image such as may be obtained using some virtual realitydisplay devices). For convenience of discussion, the examples hereinassume that cuts are introduced during the procedure of producing theflattened reconstruction. In some embodiments, the discontinuity isintroduced such that it separates (by being introduced between) twoportions of the flattened 3-D model which correspond to two differentand adjacent portions of the curved body tissue surface before thetransformation.

The resulting flattened reconstruction, and/or a view thereof may beconsidered as “quasi 2-D”; with the understanding that “quasi” indicatesthat a 3-D representation of relative feature depth (e.g., distance froma reference point) is retained.

In some embodiments, a “view” of a flattened reconstruction comprises a2-D or 3-D image showing the flattened reconstruction. The view isoptionally considered as either of the image as such (e.g., a digitalimage in computer memory), and a display and/or other representation(e.g., a printout and/or 3-D printed object) of the image.

It is noted that the flattened reconstruction may, in some embodiments,be produced piecewise as a set of intermediate results by applying afunction iteratively to portions (e.g., individual data points) of thesource reconstruction, e.g., in the course of producing an image oranother view showing the flattened reconstruction. In such embodiments,the flattened reconstruction is not necessarily stored in computermemory all at once. For purposes of the descriptions and claims herein,the aggregate of intermediate results in such embodiments also should beconsidered as comprising a “flattened reconstruction”, and alsoequivalent to a storage in computer memory of a flattened reconstruction(wherein the scope of the term “computer memory” includes on-boardprocessor registers), albeit optionally serially. Any given intermediateresult of producing the flattened reconstruction should also beconsidered as comprising a “flattened reconstruction” and a storage incomputer memory of a flattened reconstruction, albeit a partial one.

The relative flattening, in some embodiments, creates a substantiallyflat surface (that is, of practically zero curvature, or curvature muchsmaller than the source reconstruction had). In some embodiments, theflattening retains some global curvature. Optionally, a measure of theflattening may be expressed as an increase in the radius of a spherewhich best fits (e.g., minimizes average distance to) the flattenedreconstruction, compared to the best-fit sphere for the source 3-Drepresentation of the surface. The radius increase is determined forsubstantially unchanged sizes of surface features (e.g., the same onaverage). In some embodiments this radius increase is at least a factorof 2, and preferably at least a factor of 5. Optionally, the best-fitsphere for the source 3-D representation is considered to define theglobal curvature which is relatively flattened.

The curved body tissue surface extends, in some embodiments, at least135°, 180°, 270°, and preferably 360° around the reference point. Thereference point should be understood near the middle of (e.g., withinthe central 50% of) a volume around which the curved body tissueextends. For example, for purposes of determining angular extent of thecurved surface: the curved surface, in some embodiments, is best-fit bya sphere having a radius smaller than about twice the minimum distancebetween the surface and the reference point. Additionally oralternatively, the reference point around which the curved surfaceextends is located within the best-fit sphere having a radius r, at adistance less than r/2 from the center of the best-fit sphere.

In some embodiments, a flattened reconstruction is flattened over alarge region of a complete source reconstruction (e.g., at least 70%,80%, 90%, 95%, or another fraction of the surface in the sourcereconstruction—that is, the shape of the surface—optionally covering atleast 2π, 2.5π, 3π, 3.5π or 4π steradians of solid angle from areference location within the source reconstruction). Modeling in theflattened 3-D model may comprise substantially all of the shape of thesurface of a body cavity represented in the source 3-D model. Theflattened reconstruction view is optionally of the whole flattenedreconstruction, and/or of any suitable portion of the flattenedreconstruction (e.g., less than 70%, less than 50%, or anotherfraction). Optionally, the view zooms up to a particular feature such asa pulmonary vein ostium, or even is adjusted to viewpoints from withinthe relief details (e.g., blood vessels) themselves. In someembodiments, a region within the flattened reconstruction which isparticularly targeted for display with low angular and/or distancedistortion comprises a plurality of regions (optionally contiguous orseparate) spaced from each other (in a corresponding sourcereconstruction, and with respect to a reference point) by at least 90°,at least 120°, at least 135°, at least 150°, or at least another angle.

In some embodiments, distortion of distances within the targeted region(e.g., in the flattened reconstruction itself, and/or comparing twofeatures of identical size in corresponding views of curved andflattened reconstructions) comprises relative distance distortions ofless than about 1%, less than about 3%, less than about 5%, less thanabout 10%, less than about 8%, or less than another larger, smaller,and/or intermediate number. In some embodiments, distortion of angleswithin the targeted region (e.g., differences of represented angle forlines running parallel to each other in a corresponding 3-D field ofview) comprises angular distortions of less than about 1°, less thanabout 3°, less than about 5° less than about 8°, less than about 10°, orless than another larger, smaller, and/or intermediate angle. In someembodiments, at least 70%, 80%, 90%, 95%, 98%, or another amount oftotal angular and/or distance distortion (e.g., relative to a referencesize and/or angle chosen from within the target region) is concentratedoutside of the target region. In some embodiments, the relativeconcentration of total angular and/or distance distortion (averagedistortion per unit area with respect to a reference size and/or anglechosen from within the target region) is in a ratio of at least 4:1,5:1, 10:1, 20:1, or at least another ratio, with the target area havingthe smaller relative concentration of distortion compared to regionsoutside the target area. In some embodiments, the targeted regionsthemselves subtend (in total area, whether or not contiguous) at least15%, 25%, 33%, 40%, 50%, or another fraction of the total representedarea in the flattened reconstruction view.

In some embodiments, distortion amounts on surfaces in the flattened 3-Dmodel (e.g., amounts of distortion in terms of percent change in sizecompared to the source 3-D model) are substantially the same (e.g., interms of percent difference in size) across straight linear regions ofthe flattened 3-D model, e.g., moving from one side of the model to theother. In some embodiments, a user is given means to manage distortionsduring flattening; for example, choosing where key positions such ascuts are to be made, and/or

A reconstructed curved body tissue surface comprises, for example, aninner surface of a body lumen (e.g., a heart chamber, blood vessel,lymph vessel, bone, membrane, cyst, gastrointestinal tract portion,kidney/urinary tract portion, respiratory tract portion, reproductivetract portion, eye, ear, CNS ventricle, peritoneum, and/or anothernatural and/or artificial space such as implant surroundings) and thereference point is located near the middle of the reconstructed bodylumen. In embodiments disclosed herein, the left atrium is used as anexample of a particular hollow organ (body cavity) to which such avisualization method is optionally applied. However, it should beunderstood that the technique optionally applies, changed as necessary,to the interior of any hollow organ or portion thereof. In someembodiments, a representation of an organ exterior surface (e.g., of aheart, liver, kidney, brain, and/or portion(s) thereof such as a rightatrium) is flattened.

In some embodiments, atrial fibrillation is to be treated with ablationsin the left atrium (LA), by formation of one or more closed lines oflesions which substantially isolate one or more pulmonary veins (PV)from surrounding cardiac tissue to which they are connected. In atypical procedure, a goal is to isolate all PVs this way. An individualablation line may encircle one PV, or a plurality of PVs.

Simultaneous viewing of a large portion of a curved surface of a bodyportion has potential advantages for presenting a unified impression ofa region targeted, e.g., for treatment delivery. However, withouttransformation of a source representation to a flattened representation,gaining such a simultaneous view raises different potential problems.

For example, with respect to ablation treatments of PVs in the LA: whenthe LA is viewed in 3-D through a typical field-of-view angle (e.g.,subtending 60°, 50°, 40°, 30° or less), some variable part of theregions to be isolated may be persistently hidden and/or variablydistorted, no matter what view direction is chosen. From vantage pointsclose to the LA wall, target details are potentially out of the field ofview. From vantage points far from a target side of the LA wall, butstill “within the lumen”, some target details may still be out of thefield of view, and/or distorted due to curvature of the lumenal wall.With a larger angular field of view, more target details may becomeapparent, but with increasing distortion near the edges of the field ofview—distortion that would potentially change significantly if thecenter of the field of view was moved. From a vantage point outside theLA (e.g., making a proximal wall transparent so that interior targetdetails of a more distal wall can be seen), some target details may behidden by the transparency, and/or foreshortened so as to make themdifficult to distinguish.

Moreover, simulated lighting used in defining (e.g., rendering to a 2-Dimage) a view of a reconstruction may include shading (shadow) effectsto provide a sense of depth. But shading of a curved surface simulatinga fixed light source position may result in some features beingrelatively over-lit or under-lit, depending on their general position,making comparisons difficult. Changing the light source, on the otherhand, can result in dramatic (and potentially disorienting) changes tothe appearance of the features.

Practically, in order to ablate around the PVs while maintaining a viewof the working area, views from a simulated internal camera vantagepoint are commonly kept near to a “natural” field of view angle (e.g.,30°-60°, and/or similar to the angular size of the display). The vantagepoint is rotated to look at new portions of the targeted region asnecessary. The number of rotations used under such conditions istypically about 8 times for closing a circle around one PV. In practice,this is commonly carried out by an assistant physician or technologist,who moves the view according to the request of the operating physician.A potential drawback of this method is that it may require extrapersonnel in the room, with attendant potential extra expense, trainingrequirements, scheduling requirements (e.g., to make sure personnel areavailable simultaneously), and/or procedure complexity.

An aspect of some embodiments relates to the use of displays offlattened representations of body tissue surfaces. The use optionallycomprises updating of the flattened representation during mapping usingdata collected from an intrabody probe, and/or guidance of navigation ofthe intrabody probe itself, shown moving within a scene (space)comprising the flattened reconstruction.

In some embodiments, a position of an intrabody probe is transformedfrom source coordinates into a new set of coordinates which are used toindicate a position of the intrabody probe together with a view of theflattened reconstruction.

In some embodiments, a flattened reconstruction and/or one or more viewsthereof is created and iteratively updated during an interactiveprocedure that repeats the transformation and image production/displayfrom data acquired while a measurement-making catheter probe isnavigated (moved) in the vicinity of the body surface represented, e.g.,within a lumen bounded by the body surface.

In some embodiments, the updating comprises changing the flattenedreconstruction to include new surface position data, e.g., position datadetermined using measurements (e.g., electrical, magnetic, and/orultrasound measurements) made from the catheter probe itself. Thisinclusion may be implemented by updating the source reconstruction andtransforming it to provide an updated flattened representation, and/orby transforming the new data and adding the new data transformeddirectly to the existing flattened reconstruction. Optionally, updatingis automatic and optionally continuous as new position data is acquired.Optionally, updating is manually instigated and/or can be manuallypaused, e.g., for stability of display during a critical phase of aprocedure.

Optionally, indications of events (such as ablation points) and/ormeasurements other than surface positions (such as functional data) areshown together with the flattened reconstruction, optionally shownupdating as new events occur and/or measurements are collected.

In some embodiments, updating is performed using only a portion ofavailable position data. For example, by omitting earlier data, theremay optionally be obtained a flattened reconstruction view whichindicates a current state of a surface which may have changed overtime—such as different blood vessel diameters, changes in heart chambersize due to an arrhythmia, or another changing feature. Optionally,available data is selected for inclusion in the flattened reconstructionusing gating, e.g., to a particular phase of respiration and/orheartbeat.

Additionally or alternatively, in some embodiments, the updatingcomprises changing a view created from the flattened reconstruction,e.g., by changing a view angle, distance, or other viewing parameter.Optionally, view changes occur automatically, for example, in responseto events of a catheter procedures such as approaching and/or contactingrepresented tissue surfaces. Additionally or alternatively, in someembodiments, view changes are manually controlled by an operator.

In some embodiments, showing the surface to be treated in a single,suitably flattened reconstruction view provides a potential advantage bypermitting operability of the system by a single operator engaged innavigation of an intrabody probe (e.g., a catheter probe).

Optionally, a view of the flattened reconstruction is defined initiallyfor a procedure, e.g., a procedure performed within a certain bodycavity, and after this the whole body cavity surface can be seen at onceas navigation within the body cavity is performed using an intrabodyprobe, without a need for further viewing parameter adjustments (thoughoptionally the flattened reconstruction and view are interactivelyupdated with new data describing the body cavity surface as it becomesavailable).

Optionally, flattened reconstruction and source reconstruction views aredisplayed simultaneously during intrabody probe navigation (optionally,just the flattened reconstruction is shown in a view). In someembodiments, shifting between flattened and source views is easilycontrolled by a single user (e.g., using a foot-pedal, and/or triggeredby a position of a catheter probe). The transition is optionally smooth,e.g., comprising “unrolling” from the source reconstruction to theflattened reconstruction, and optionally “rolling” back again.Additionally or alternatively, this may be described as producing viewsof a series of reconstructions flattened over a range of increasingaverage radii of curvature. The smooth transition potentially helps topreserve a sense of object constancy.

In some embodiments, triggering of the transition and/or another aspectof the current view is controlled automatically by an algorithm based oncurrent conditions. In some embodiments, a 3-D view is from theviewpoint of the catheter (e.g., so that no part which is about to betreated is hidden from view). In some embodiments, a 3-D view is from aviewpoint facing a site to be treated, does not follow movements of thecatheter. The catheter movement, however, may be symbolicallyrepresented on the 3-D view. In some embodiments, the site to be treatedis marked by the physician on the flattened reconstruction view, and theflattened reconstruction view is switched automatically to a 3-D viewfacing the marked site, e.g., when the catheter approaches the markedsite or when the physician requests such a switch, e.g., by pressing apedal. Parameters considered in automatically switching between viewsoptionally include, for example, distance from a tissue wall, headingdirection, phase of procedure (e.g., between two different sub-lesionablations within a single ablation line, and/or switching between twodifferent ablation lines).

In some embodiments, for example, a switching algorithm is configured topresent the overview of a flattened reconstruction view when a catheterprobe is navigated by the user far from a tissue wall, and a 3-D viewwhen the user is near the tissue wall, and/or actively engaged intreatment such as ablation.

In some embodiments, the use of manual view switching by one or moreusers is monitored, and used as input to train a machine-learningalgorithm what view is preferred under different circumstances.Optionally, machine-learning is performed using input from users ofdifferent stages of experience, and/or exhibiting different clusters(e.g., statistical clusters based on differences in selected view as afunction of probe position and/or other procedure parameters) of usestyle, so that an operator may be presented with choices of automaticview switching which best suit their own mode of use.

An aspect of some embodiments of the present disclosure relates to thedetermination of an orientation of a source reconstruction, optionallyin preparation for the production of a flattened reconstruction.

In some embodiments, an anatomical orientation of a reconstruction(e.g., a source reconstruction) is determined, for example as part ofthe process of producing a flattened reconstruction. This may be useful,for example, when the general anatomical origin of data represented in asource reconstruction is initially known (e.g., the data describe aninner lumen of a left atrium); but there remains unknown, unclear,and/or approximate certain specifics of how the reconstruction isoriented; e.g., with respect to landmark features of the anatomy.Moreover, even when orientation is well-known with respect to somereference coordinate system, variations in individual anatomy can affectwhat orientation framework is preferable for generating a flattenedreconstruction, and/or a display of a reconstruction.

In some embodiments, orientation is determined based on one or moremetrics of surface regions, determined from a 3-D representation thesurface (optionally either a flattened or un-flattened representation).In some embodiments, the metrics are based on depth and/or distanceinformation. For example, positions more distant from some referencepoint are given a different (e.g., larger) weight than positions closerto the reference point. The weights are then used in combination withone or more rules in order to determine an orientation. For example,where relatively deep (more distant, and, e.g., receiving more weight)features of interest (and/or clusters thereof) are expected to fallalong a common line, a rule may specify that this common line providesan orienting reference. In another example, a rule may specify that aline at a position where weight on two sides is balanced providesanother orienting reference. Further rules may apply, for example, toresolving potential ambiguities (e.g., where two or more positionssatisfy some criterion). Once the orienting references are determined,they are optionally used for purposes of orienting display ofreconstruction views. In some embodiments, positions at whichdiscontinuities (cuts) are to be introduced during the flattening of asource reconstruction are determined based on the orienting references.

The rules defined and used optionally vary according to thecharacteristic anatomy of different anatomical locations. For example,rules applicable to the left atrium optionally take into account thetypical positions and/or clusterings of the pulmonary veins, left atrialappendage, and/or mitral valve. Rules applicable to the right atriumoptionally take into account the typical positions and/or clusterings ofthe superior and inferior vena cava, the coronary sinus, and/or thetricuspid valve.

Before explaining at least one embodiment of the present disclosure indetail, it is to be understood that the present disclosure is notnecessarily limited in its application to the details of constructionand the arrangement of the components and/or methods set forth in thefollowing description and/or illustrated in the drawings. The presentdisclosure is capable of other embodiments or of being practiced orcarried out in various ways.

Flattening of a Reconstruction of a 3-D Lumenal Shape

Reference is now made to FIG. 1A, which schematically representsanatomical features of a left atrium 2 represented in its usual 3-Dshape, according to some embodiments of the present disclosure. In FIG.1A, Left atrium 2 is represented as a globular shape.

Locations of the roots of pulmonary veins 10 and mitral valve 12 areshown. Also represented is ablation line 14, the two halves of whichtogether encircle the roots of the left-most two pulmonary veins 10. Thenearer half and further half of ablation line 14 are represented withdifferently dotted lines.

Also shown are arrows 11A, 11B and reference points 21, 22 23, furtherreferred to in the descriptions of FIG. 1B.

Further reference is now made to FIG. 1C, which shows a reconstructionof a left atrium 2 represented in its usual (un-flattened) 3-D shape,according to some embodiments of the present disclosure.

Mitral valve 12 and roots of pulmonary veins 10 are also shown in FIG.1C, along with left atrial appendage (LAA) 15. Also shown are arrows11C, 11D, 11E, and reference point 21, which are further referred to inthe descriptions of FIG. 1D.

FIGS. 1A and 1C indicate lines 13A and 13, respectively, along which the3-D lumenal shape of left atrium 2 is opened (that is, virtually cut,introducing a discontinuity) to produce the flattened reconstructionviews of FIGS. 1B and 1D. It should be noted that Lines 13A and 13 arerepresented somewhat differently upon flattening, as explained inrelation to FIGS. 1B and 1D.

For orientation, reference points 21 of FIG. 1A and FIG. 1C are shown inFIG. 1B and FIG. 1D at the respective center of each flattenedreconstruction view.

Reference is now made to FIG. 1B, which schematically representsanatomical features of a left atrium 2 spread out into a flattenedshape, according to some embodiments of the present disclosure. FIG. 1Brepresents a flattened reconstruction view of the atrium 2 of FIG. 1A.

In the flattening transformation used in producing the reconstructionschematically indicated in FIG. 1B, it is approximately as though theleft atrium wall was slit partially up the center of the view of FIG. 1Aon two sides (e.g., along the lines extending upward from referencepoints 22 and 23), and unwrapped for viewing. Arrows 11A-11B of FIGS.1A-1B represent spherical angle coordinates of FIG. 1A mapped toCartesian axes of FIG. 1B. It should be noted that reference points 22,23 become the corners of the flattened reconstruction view. The positionof the mitral valve 12 is located off the edges of the view, so that thetwo lateral boundaries of FIG. 1B (extending between points 22 and 23)correspond to the circumference of mitral valve 12. Cut lines 13A areoriented across the top and bottom of the view of FIG. 1B.

In the flattened reconstruction view of FIG. 1B, the entirety ofablation line 14 is now visible at once, and from the same side. Thisillustrates a potential advantage of the flattened reconstruction view,insofar as more of the interior surface of the left atrium 2 can be seenin a single flattened reconstruction view. Another potential advantage,in some embodiments, is that a catheter probe remains in the image as itmoves in the vicinity of any portion of the ablation line, since thereis optionally also represented in a view a volume above the flattenedreconstruction, into which a representation of the catheter probe may beplaced.

Further reference is now made to FIG. 1D, which is a view of a flattenedreconstruction flattened from the source reconstruction of FIG. 1C,according to some embodiments of the present disclosure. In FIG. 1D, aslightly different transformation from that of FIG. 1C is used. In thisflattened reconstruction, the small regions 16A, 16B of FIG. 1C arestretched along the lower and upper boundaries of the view, while theedges produced by cut 13 extend along the lateral sides of thisflattened reconstruction view. Additionally to features such as themitral valve 12, the pulmonary veins 10, and the left atrial appendage15, the trans-septal 17 (at the position of the fossa ovalis) is alsoshown.

It is noted that despite the transformation that “flattens” thereconstruction of FIG. 1C, relative positions in depth of surfacepositions are retained in the flattened reconstruction. Thereconstruction is re-encoding of co-ordinates defining the source 3-Dshape, (e.g., the shape displayed in FIG. 1C) to a transformed andflattened 3-D shape (e.g., the shape displayed in FIG. 1D).

Transformation from Source Reconstruction to Flattened Reconstruction

Reference is now made to FIG. 1E, which is a flowchart outlining amethod of producing an image of a flattened reconstruction, according tosome embodiments of the present disclosure.

At block 102, in some embodiments, a source reconstruction comprising a3-D representation of a curved body tissue surface is received.

At block 104, in some embodiments, a flattened reconstruction isproduced from the source reconstruction. The flattened reconstruction isproduced so that a global curvature (that is, a curve defined over thearea of the curved surface, but not following all its details) isreduced. The global curvature is the curvature of a curve defined overthe area of the curved surface, but not following all its details. Forexample, it may be the curvature of a sphere or of an ellipsoid,best-fitting the curved surface. Optionally, the global curvature isimplicit, e.g., in the choice of coordinate systems used in a flatteningtransformation.

At block 106, in some embodiments, an image is produced using theflattened reconstruction.

Further reference is now made to FIG. 1F, which is a flowchart outlininga method of producing a flattened reconstruction, according to someembodiments of the present disclosure.

At block 110, in some embodiments, a source reconstruction comprising a3-D representation of a curved body organ surface is received. Thesource reconstruction may be conceptualized as including a surface(which may be smooth or not) of a global curvature and relief detailsdistributed along the surface of global curvature (e.g., detailsrepresented by 3-D positions on the curved body organ surface which areat some distance from a surface representing the surface of globalcurvature).

At block 112, in some embodiments, the relief details are isolated fromthe surface of global curvature.

At block 114, in some embodiments, a flattened reconstruction isproduced for storage in computer memory, using the isolated reliefdetails. In some embodiments, the computer memory stores the flattenedreconstruction as new copies of coordinates of points composing therelief details directly. The coordinates of the points composing therelief details may compose flattened relief details obtainable, in someembodiments, by the flattening transformation described above, e.g., inthe context of block 104 of Figure JE. Optionally, the global curvaturewhich was flattened out of the source reconstruction to produce theflattened reconstruction is also stored. In some embodiments, what isstored comprises an indication of the transform used to produce theflattened surface of reduced global curvature from the sourcereconstruction, associated by processor instructions to the sourcereconstruction. For example, a rendering program is configured tointerpret source reconstruction stored as coordinates of (r,θ,φ) ascoordinates of (z,x,y).

In some embodiments, FIGS. 1E and 1F comprise alternative descriptionsof the same method of producing a flattened reconstruction of a curvedbody tissue surface.

Input data for producing the source reconstruction optionally comprisedata expressed in Cartesian coordinates obtained from 3-D imaging of thepatient, for example, CT imaging. Optionally, the data come from anothermethod, for example, using intrabody mapping of positions of a catheterprobe (e.g., an electrode probe, magnetic probe, and/or ultrasoundprobe). In some embodiments, data representing a lumenal wall of a bodycavity are obtained using a remote electrical field imaging method, forexample a method described in U.S. Provisional Patent Application No.62/546,775 entitled FIELD GRADIENT-BASED REMOTE IMAGING, and filed Aug.17, 2017; the contents of which are incorporated herein in theirentirety.

In some embodiments, data representing a lumenal wall of a body cavityare obtained using a reconstruction method described in U.S. ProvisionalPatent Application No. 62/445,433 entitled SYSTEMS AND METHODS FORRECONSTRUCTION OF INTRA-BODY ELECTRICAL READINGS TO ANATOMICALSTRUCTURE, and filed Jan. 12, 2017; the contents of which areincorporated herein in their entirety. Use of mapping by intra-bodyprobe, e.g., as disclosed in the above two provisional patentapplications, provides a potential advantage by allowing data for aflattened reconstruction of a body surface to be collected on the fly(e.g., in real time) as a catheter probe (optionally a standard ablationcatheter probe) enters a body region bounded by the body surface. Theabove cited provisional applications may even provide the ability tocollect on the fly data pertaining to structure of regions which havenot necessarily been visited by the probe. Optionally, reconstruction isperformed using field gradient-based remote imaging, without the use ofauxiliary image data.

Use of this surface imaging method provides a potential advantage byallowing data for a flattened reconstruction of a body surface to becollected on the fly (e.g., in real time) as a catheter to probe(optionally a standard electrode catheter probe) enters a body regionbounded by the body surface, including collection from regions whichhave not necessarily been visited by the probe. Optionally,reconstruction is performed using field gradient-based remote imaging,without the use of auxiliary image data.

In a first example embodiment of producing a flattened reconstruction,the 3-D representation of the source reconstruction is first encoded(e.g., from Cartesian coordinates) into spherical coordinates; e.g.,(x,y,z) coordinates are transformed using a spherical coordinatetransform to coordinates expressed as (r,θ,φ), where r is a radius, andθ and φ are spherical angles. This intermediate result comprises achange in coordinate system, without yet introducing a change in theshape of the source reconstruction. Optionally there is a rigidtransform applied as part of the conversion, e.g., to set an origin nearthe center of a lumen defined by the reconstructed surface, and/or toset an orientation along which a discontinuity (cut) will be introducedas part of the flattening.

In some embodiments, to next create the flattened transformation (inoverview): the x (horizontal) dimension of the flattened representationis mapped to one of the two angular coordinates (e.g., θ, representingazimuthal angles, in a range, e.g., from 0° to 360°). The y (vertical)dimension is mapped to the other (e.g., φ, representing inclinationangle, in a range, e.g., from 0° to 180°, or −90° to +90°, depending onthe 0-angle convention adopted). The z (depth) dimension is optionallydirectly substituted with r. In some embodiments, this mapping may beunderstood as analogous to projection of angular coordinates onto acurved surface, for example a cylinder, cone, or other surface—exceptthat local relative distance information is retained so that theresulting projection does not smoothly follow the cylinder, cone, orother surface.

In this flattening method, the sizes of r depend on the chosen origin(e.g., at the stage of conversion to spherical coordinates). The originis chosen, in some embodiments, so that distances to points on thecoronary wall which are about equidistant along the wall to themidpoints of each pair of pulmonary veins are also shown aboutequidistant to this reference in the flattened image (practically, thistends to locate the origin near the geometrical center of the leftatrium). In some embodiments, the origin is dynamically changed,according to a current focus of work (e.g., set by the position of probe31). For example, the origin optionally shifts to give the leastdistorted available view of a region which is closest in position to acurrent position of the catheter probe.

It is noted that if r is directly mapped to z, this is similar tosetting a(θ,φ)=0 in the framework of the following alternativeembodiment of a transform from source reconstruction to flattenedreconstruction. There is still a global curvature, however, implicit inthe choice of coordinate system. This will be discussed after thefollowing indirect transformation method of converting r to z isexplained.

In some embodiments of the flattening (block 104) and/or isolating andproducing (blocks 112, 114), the source reconstruction is optionallymodeled as r(θ,φ); comprising the sum of two terms, each of whichdescribes distances to the surface from some reference point as afunction of spherical angle coordinates, e.g.:

r(θ,φ)=a(θ,φ)+b(θ,φ)

Here and in the following descriptions, θ may be considered as theazimuth angle, and φ as the polar (inclination) angle.

The first term a(θ,φ) describes the global curvature as any suitablesmooth geometrical object (e.g., a sphere, ellipsoid, parametric curve,combination of spherical harmonics, and/or long wavelength frequencydomain components of a Fourier transform of the surface transformed backinto the spatial domain). The object and/or its degree of smoothness isoptionally determined by structure (e.g., the angular size) of detailswhich are to be preserved or suppressed. For example, insofar as thefirst term follows the curvature of a detail in the sourcereconstruction, that detail will tend to be suppressed in the flattenedreconstruction. The parameters of the smooth geometrical object may bechosen, for example, as those that best fit (e.g., minimize differencesin distance, minimizes variance, minimize some weighted combination ofthe two, or best satisfy according to another criterion) the sourcereconstruction r(θ,φ).

The first term a(θ,φ) gives the distance of the smooth object's surfacefrom the reference point as a function of spherical angle. The secondterm b(θ,φ) describes the relief details. The second term may be derivedas the mathematical difference (by subtraction) of a representation ofthe source reconstruction in spherical coordinates and the first term,for example:

b(θ,φ)=r(θ,φ)−a(θ,φ)

So-defined, the second term b(θ,φ) provides, at each spherical angledefined by the source reconstruction, the extra/reduced distance fromthe reference point to the surface of the source reconstruction,compared to the distance from the reference point to the surface of thesmooth geometrical object provided as a definition of the globalcurvature.

In some embodiments, producing the flattened reconstruction (“flatteningthe source reconstruction”) comprises a lookup operation that re-plotsthe second term b(θ,φ) into Cartesian coordinates. For example,z(x,y)=b(Θ_(x),Φ_(y)); wherein x and y are used as lookup variablestransformed by the functions Θ_(x) and Φ_(y) to the defined ranges of θand φ. The assignment effectively determines where “cuts” will be madeto allow unrolling the source representation into the flattenedrepresentation.

This operation produces a flattened reconstruction which preserves(albeit typically with some kind of distortion, e.g., stretching, sizechange, and/or local angle change), the relief features of b(θ,φ), andis planar with respect to the global curvature (e.g., if r(θ,φ)=a(θ,φ),then b(θ,φ)=0, and z(x,y)=0).

This particular method introduces some distortion in the flattenedreconstruction. For example, the path in the source reconstruction ofthe equatorial circumference (when θ=0) is much longer than the lengthof its parallel paths as

$\left. \theta\rightarrow\frac{\pi}{2} \right.,$

but the two paths are represented as having equal length in theflattened reconstruction just explained. Some level of distortion and/ordiscontinuity is generally unavoidable when converting curved 3-Dsurfaces to flat (in 3-D space) representations, but the nature of thedistortions/discontinuities can be controlled, e.g., to preserverelative areas, directions, and/or distances. For example, the relativescale of the x and y axes comprises a parameter that may be set. In someembodiments, the ratio is set so that it most closely approaches 1:1 inthe regions of the pulmonary veins.

Optionally, one or more cartographic techniques used to controldistortions, e.g., of land masses in flat maps of a globe, are used tocontrol distortions of representation in the (x,y) plane relative to a(optionally spherical) global curvature. With the framework justdescribed, this could be generally implemented by making the lookupfunctions dependent in any suitable fashion on both x and y (e.g.,Θ_(x,y) and Φ_(x,y)), or by another method producing equivalent results.In some embodiments, distortion is controlled so that targeted portionsof the body tissue surface are presented with relative reduceddistortion; e.g., portions targeted for treatment.

Other methods and/or results of flattening are possible. For example abowl-shaped or other non-planar flattened reconstruction can be obtainedby choosing a global curvature term a(θ,φ) which is suitably differentfrom a best-fitting smooth shape, and/or by using an offset term whenproducing the flattened reconstruction, e.g., asz(x,y)=b(Θ_(x),Φ_(y))+c(x,y). Non-planar flattened reconstructionsprovide a potential advantage for allowing reduction offlattening-related distortions, while still exposing a larger surface tosimultaneous viewing. However, insofar as a view of a flattenedreconstruction eventually targets viewing by the human eye—with all itsinherent limitations on field-of-view perception—taking full advantageof this potential advantage may require special arrangements formovement of the reconstruction in the view, and/or for immersivedisplay.

In another example of flattening: in some embodiments, a longitudinallyextended and convoluted organ (e.g., an intestine or blood vessel) isrendered in straightened form. A smooth geometrical object used todefine a global curvature in such embodiments is optionally an extrusionof a planar figure (e.g., a circle or ellipse) along a parametric path(e.g., a Bézier curve) that follows a centerline of the convolutedorgan. Optionally, the planar figure is itself variable as a function ofdistance along the parametric path. The coordinate system used may beother than spherical, for example, a type of cylindrical coordinatesystem, wherein distance along the parametric path is used as a linearaxis, and position around the parametric path is expressed as a polarcoordinate combination of angle and distance (radius).

Whether these sorts of transformations are suitable optionally dependson the types of navigation and/or navigation controls available. Forexample, inside-out inversion of an exterior surface may be suitable fora beam-type treatment system where the beam may be directed fromsubstantially any location, so that the user always feels as though thebeam is coming from a central point. Optionally, treatment in an organwhere navigation is substantially push-pull (e.g., navigation of anendoscope through an intestine) is aided by rendering of a view as amore straightened version of actual 3-D geometry.

In a special case, if the first term a(θ,φ) is defined as for a spherecentered at the spherical coordinates origin, then a(θ,φ)=k, where k isthe constant radius of the sphere. However, the final flattenedreconstruction is insensitive to the choice of k in this condition. Fora spherical global curvature centered on the spherical coordinate'sorigin, every choice of k produces a substantially equivalent result,except that there is a relative offset of the flattened reconstructionby a distance along the z axis controlled by k.

In the first transform method described in this section (where r isdirectly mapped to z), it was noted that the result is similar tosetting a(θ,φ)=0, and so, accordingly, k=0. This 0-radius sphere is notan indication of “no global curvature”, but rather, is possible becauseof the particular (spherical) model of global curvature inherent in thechoice of coordinate system. The global curvature is defined asspherical, albeit implicitly, and is still being removed (even with k=0,since all values of k lead to flattening in this special case, making itunnecessary to specify one in particular).

In converting a flattened reconstruction to a 2-D image (e.g., 2-D indisplay coordinates), providing a flattened reconstruction view, depthinformation can be indicated, for example, by orientation-dependentshading of surfaces, and/or by changing the parallax of viewed featuresdepending on the relative positions of the viewpoint and the flattenedreconstruction.

For example, distances in FIG. 1C from a reference point 24 internal toleft atrium 2 (e.g., a point half-way between reference point 21 and theapex representing valve 12) are transformed in the flattenedreconstruction shown in FIG. 1D to a Cartesian axis of image depth. Thisaxis is indicated by arrow 11E.

It should be noted that the flattened reconstruction of FIG. 1D isdisplayed as though viewed from an offset angle, which potentiallyserves to highlight certain features (e.g., allow viewing intoapertures). Slight changes to the offset angle potentially serve toemphasize differences in depth (e.g., due to parallax changes). Angularpositions in FIG. 1C relative to reference point 24 are transformed inthe reconstruction of FIG. 1D into the two remaining Cartesian axes,e.g., Cartesian axes extending along arrows 11D and 11C.

It is emphasized that while the flattened reconstruction, in someembodiments (e.g., FIG. 1D) is reminiscent of certain types ofcylindrical map projections, the retaining of transformed depthinformation allows the result to optionally be viewed from any displayangle, with resulting shifts in parallax and/or angles affecting featurepresentation (e.g., angles interacting with simulated lightingconditions). A traditional 2-D projection of a 3-D surface does notretain such information (this is discussed further, e.g., in relation toFIGS. 7A-7B, herein).

The flattening (curve-straightening, unrolling) type of transformationpresented by examples in FIGS. 1A-1D has potential advantages for use inintracardial navigation of a catheter probe (for example, an ablationprobe). First, the transformed reconstruction is suitable to lay out inone view an extended surface area which may be a target of measurementand/or treatment procedures. Second, at the same time, the flattenedreconstructions optionally preserve a relatively undistorted appearanceof surfaces throughout a large target region, for example, in the regionof the roots of the pulmonary veins 10. This is particularly ofpotential benefit for procedures comprising the formation of one or morelines of ablation to electrically isolate the pulmonary veins fromsurrounding cardiac tissue. In other embodiments, other targets may beselected, for example, other portions of the 3-D object to berepresented may be viewed with minimal distortion.

Another potential advantage is that because the flattened representationremains 3-D in character, it defines a volume into which indicationsrelated to catheter probe position can be placed, for example, a probeicon or other indication at the probe's current position, includingindications that correctly indicate contact with the flattenedrepresentation surface.

While a probe position could be placed in a scene together with a sourcerepresentation before rendering to a typical camera-view type 2-D image,the probe appearance would itself be subject to, e.g., perspectivedistortions, which could be quite disturbing, e.g., at the edges of afisheye view. On the other hand, once a 2-D image of the surface isrendered, some 3-D information is lost (e.g., indicated instead byartificial depth cues such as shading and self-masking), so that it isdifficult to accurately reintroduce the probe tip position into thescene e.g., so that probe contact with the flattened surface atdifferent depths is correctly shown. Also, 2-D image will tend tosuppress detail where there is more than one layer (e.g., blood vesselsbranching beyond a lumenal surface of a heart chamber).

Setting of the Cut Line

In some embodiments, remaining parameters of the flattening includewhere to make the “cut” (e.g., represented by the lines 13A extendingfrom reference points 22 and 23 in FIG. 1A, and/or line 13 in FIG. 1C).

Reference is now made to FIG. 1G, which is a flowchart outlining amethod of determining an orientation of a reconstruction of a curvedbody tissue surface, according to some embodiments of the presentdisclosure.

At block 120, in some embodiments, relief details are received. Theserelief details may be the isolated relief details of block 112.Optionally, relief details are provided together with the globalcurvature, in which case the operations of block 122 are optionallyadjusted to discount effects of global curvature on the weighting ofrelief details.

At block 122, in some embodiments, weightings are assigned to the reliefdetails. Optionally, the weightings are assigned according to distanceand/or depth (“amplitude”) of relief details, relative to a referencepoint, reference offset, and/or reference curvature (e.g., a suitableglobal curvature definition). Weightings can be directly proportional torelief detail amplitude, linearly related, related as a power function,or provided as some other function of relief detail amplitude.

At block 123, in some embodiments, orientation of the relief details isdetermined, using criteria applied to the weightings assigned at block122.

With continued reference to the method of FIG. 1G: it has been notedalready that the “cut” applied in the production of FIG. 1D (representedby line 13) is oriented to pass through the center of mitral valve 12.The rotational orientation of the line also affects the flattenedreconstruction and/or view thereof; for example, if line 13 was rotated(about a vertical axis) by 90°, then the layout of features in FIG. 1Dwould also be rotated by 90°, with corresponding shifts indiscontinuities and other distortions.

With respect to flattened reconstructions of the left atrium innersurface, the inventors have found that the cut orientation shown resultsin a flattening which presents surface features in a way that isconvenient for navigation of an intracardial catheter probe (at least,for common anatomical variants). The zones of greatest distortion and/ordiscontinuity near the mitral valve 12 are also zones where catheternavigation is potentially complicated by strong and variable currents ofblood flow. Moreover, since the valve is anyway moving all the time, thereconstruction in that region anyway is potentially less accurate and/orinteresting for purposes of targeting by the catheter. Moreover, thezones 16A, 16B which have the greatest stretch-distortion are alsopositioned away from regions where features of particular interest forsome treatments, such as the pulmonary veins 10 and the LAA 15, formdistinct clusters.

In some embodiments, the orientation of cut 13 can be determined and/oradjusted manually, and/or automatically based on explicitidentifications of features and/or selection from a range of options.Optionally, manual controls allow adjustment of the cut position and/orof an origin used as a basis for the flattening operation (e.g., acenter of the global curvature), for example to account for individualanatomical differences.

Optionally, operation of the controls is defined over a Cartesiancoordinate space defined over the source reconstruction. These controlsoptionally separately control movement of the origin in the x, y, and zdirections (e.g., by 5 mm at a time, or another distance). Optionally,controls for elevation, roll, and azimuth control rotation (e.g., in 5°increments, or in another increment) around the x, y, and z axis,respectively. In some embodiments, changing of a control setting resultsin an immediate update of one or both of a view of the sourcereconstruction and the flattened reconstruction. Additionally oralternatively, another control set is defined, for example, controlsdefined over the Cartesian space of the flattened reconstruction itself.For example, an x axis control has the effect of panning a view of theflattened reconstruction left or right, a y axis control which has theeffect of scrolling the view up or down, and/or a z axis control has theeffect of translating the view toward or away from a perspective pointof the view. A rotational control optionally sets the cardinaldirections of the x and y axes with respect to the flattenedreconstruction. Controls are additionally or alternatively provided forand/or interpreted as adjustments to suitable parameters in a sphericalor other non-Cartesian coordinate system.

In some embodiments, automatic selection of a flattening parameter setcomprises a process of scoring a plurality of available flatteningparameter sets for properties (with respect to a particular anatomyand/or procedure plan) of angle preservation, distance preservation,and/or contiguity of representation, and choosing and/or makingavailable for choice options which score best. In some embodiments, aflattening parameter set may include indications of how and/or where tointroduce discontinuities (e.g., cuts along the edges of the flattenedreconstruction and/or view thereof), and/or what angular position shouldbe set at the center of the flattened reconstruction and/or viewthereof.

In some embodiments, the orientation is determined automatically and onthe fly, based on global characteristics of the reconstruction, andgeneral information about anatomical layout. For example, the cut 13 ispositioned, in some embodiments, to where the resulting flattenedreconstruction best balances feature depth (treated as a “weight”) as afunction of distance from the reconstruction's (x,y) center 21. Forexample, along the left-right direction (arrow 11C of FIG. 1D), thereare two clusters of relatively deeper features; so those features areset at roughly equal horizontal distances from the center. In theup-down direction (arrow 11D of FIG. 1D), the weight of each of theseclusters falls along a common center, so the features having largerdistances are weighted such that they “sink” to the middle. Optionally,the orientation of the axes themselves is set so that one axis passesalong this common center. Remaining ambiguity in setting the centerpoint (e.g., whether to cut through the mitral valve, or cut through theatrial wall opposite) is optionally resolved by choosing the alternativewith the greatest or least contiguously represented distance betweencluster positions.

Optionally, for body surfaces of different organs having differentgeneral anatomical arrangements of features of interest and/or for usein different procedures, different rules are set, and the weightings ofblock 122 used to satisfy those rules. It is noted that the rulesdescribed for FIG. 1D have the effect of naturally bringing the imageinto a left/right and top/bottom balanced distribution of features(which also happens to create a flattened reconstruction view which iseffective for displaying left atrium features related to atrial ablationprocedures). However there is optionally any suitable offset applied tobring features into suitable relative positions for a particularapplication (e.g., a valve procedure would optionally center the mitralvalve in the view), and/or anatomy (e.g., a reconstruction for use inthe right atrium optionally uses the superior and inferior vena cava aslandmarks for orientation of a flattened reconstruction view of theright atrium).

Considering the broader case of an arbitrary distribution of anatomicalfeatures of interest viewed on a flattened surface, the selection of anoptimal flattening may be made differently in different conditionsand/or for different purposes; e.g., different chambers and/or organs,and/or different therapy plans. For example:

-   -   Ablation inside the left ventricle (LV), e.g., for ventricular        tachycardia ablation, is optionally performed against the        background of a flattened reconstruction of an LV which has been        flattened using chamber-specific parameters.    -   For a left atrial appendage closure procedure, the LAA ostium is        optionally centered in a flattened reconstruction view of the        left atrium.    -   For a transseptal procedure, the fossa ovalis is optionally        centered in a flattened reconstruction view of the right atrium.    -   For an atrial septal defect and/or patent foramen ovale closure,        the patent foramen ovale and/or atrial septal defect is        optionally centered in a flattened reconstruction view of the        right atrium.    -   For coronary sinus cannulation and/or placement of a pacing        electrode, the coronary sinus is optionally centered in a        flattened reconstruction view of the right atrium.

For purposes of using a flattened reconstruction for purposes of guidingnavigation within a body cavity, it is optionally preferable for targetregions to be continuously linked (e.g., navigable between withouthaving to pass over a “cut”), while geometrical distortions of angleand/or size are pushed to regions away from target regions. Optionally,parameters governing flattening of a surface (for example, any of theparameters just described, or other parameters governing a differentflattening method) are modified during the procedure, for example, toshift distortions away from current main targets.

Optionally, there is more than one cut. A cut may be considered as adiscontinuity-type distortion which, once introduced to a projection,potentially allows greater freedom in reducing distortion somewhereelse. This provides a potential advantage where there are areas oflittle interest that can be more heavily distorted in exchange forimproved accuracy of representation elsewhere.

Flattened Reconstruction Views In Comparison to Other View Types

Features of the view of FIG. 1D in particular may be contrasted withother types of views. For example, reference is now made to FIG. 9A,which shows a planar sectioning of a 3-D representation of a body partreconstruction 900, according to some embodiments of the presentdisclosure; and to FIGS. 9B-9C, which show views looking into twosectioned portions of body part reconstruction 900, according to someembodiments of the present disclosure.

FIG. 9C shows a view looking along axis 902 (normal to sectioning plane901), and towards two of the pulmonary veins 10 and LAA 15 of a leftatrium 2. Due to the curvature of the left atrium 2, details along somelumen wall portions (e.g., those oriented substantially along axis 902)are obscured and/or considerably foreshortened. The curvature of theleft atrium 2 also makes it difficult to simultaneously get comparableimpressions of all the pulmonary veins 10 (even from one side) and LAA15 in one view: apertures of each present themselves at widely varyingangles. This potentially affects the appearance of surface shapes,and/or the lighting conditions affecting how well each feature can bedistinguished. As another example of a sectioned view: FIG. 9A shows aview after cutting by a different plane) into another section of bodypart reconstruction 900 showing different pulmonary veins 10, subject tothe same issues of curvature and/or lighting. Moreover, there isapparently no single planar sectioning which produces a sectionedportion that includes all the indicated features of FIGS. 9B and 9C in asingle clear view.

Also for example, reference is now made to FIGS. 10A-10D, which show arange of standard camera-type views of the interior of a reconstructedleft atrium, according to some embodiments of the present disclosure.

In FIG. 10A, LAA 15 and two left pulmonary veins 10C are shown in a 30°field of view (30° is the angular width of the field-of-view subtendedleft-to-right) from a perspective internal to the left atrium, andrelatively near to the atrial surface. Figure JOB shows the samefeatures, from the same position, using a 60° field of view. In bothcases, angular cropping complicates identifying at a glance exactly whatfeatures are shown, and in what the global orientation. This problem issomewhat reduced in the 60° view, however there is an added complicationthat regions near the edge of the image are compressed in the radialdirection, while being relatively spread out in the circumferentialdirection.

FIG. 10C shows the right pulmonary veins 10B (also in a 30° field ofview). The features shown are clearly different from that of FIGS.10A-10B, but on their own, they are difficult to unambiguously identify.In FIG. 1D, the field of view angle has been broadened to 60°, comparedto the 30° field of view of FIG. 1C, but this apparently does notsubstantially improve the identifiability of the features in the centralpart of the field of view, while again introducing significantdistortions of features near the image edges.

Apart from preservation of depth information in an intermediateflattened reconstruction, it should also be noted that the views of FIG.1B and/or FIG. 1D are potentially different in character than wouldpotentially be achieved, for example, by using a “fisheye lens”transformation of the source reconstruction, similar to views providedby ultra-wide-angle lenses and/or their simulations. Using computerizedimage transformation, it is possible to represent on one 2-D screen a180° view or greater-angled camera view of a surrounding visual field,optionally up to a 360° view. However, this introduces distortions whichincrease for the edges of the visual field as the field of view angleincreases (distortion potentially far beyond what is shown for the 60°views of FIGS. 10B and 10D). Potential disadvantages compared to theflattening just described in relation to FIG. 1B include:

-   -   They potentially become highly distorting of shapes and/or        angles approaching their edges;    -   Distortion is potentially not inherently controlled for features        of particular interest; and/or    -   Attachment of the view to a viewpoint could cause the        distortions change to shape constantly as the central direction        of view shifts.        Flattened Representations with Overlays

Reference is now made to FIG. 2A, which shows a flattened reconstructionview of left atrium 2 anatomy, according to some embodiments of thepresent disclosure. Further reference is made to FIG. 2B, which showsthe view of FIG. 2A, with additional markers indicating ablation points14, 14A and catheter probe 31, according to some embodiments of thepresent disclosure.

In FIGS. 2A-2B, the same anatomical features indicated in FIG. 1D andschematically in FIG. 1B are shown again based on a 3-D left atriummodel, illustrating the “relief”-type display of features which theflattened reconstruction supports.

Also shown in FIG. 2B is a representation of a catheter probe 31.Ablation line 14 is represented by balls 14A embedded in the tissuearound the pulmonary veins 10; each ball 14A optionally represents asub-lesion of the ablation line. The similarity in size of each ball 14Ais an indication of the relatively low relative distortion in theregions where they appear (each ball is rendered to be the same size in3-D).

It should be noted again that although the images of FIGS. 2A-2B areflattened compared to the actual geometry of a left atrium, somefeatures (particularly PVs) appear in 3-D relief. Optionally, thesimulated illumination is dynamic in the flattened reconstruction view,e.g., by continuous linkage to the flattened reconstruction, whichserves as a model of the 3-D scene illustrated in the view. In someembodiments, illumination effects are tied to motion of a catheter probeshown within the view, which can help provide a user with a sense ofposition of the probe in depth relative to displayed surface features.Optionally, the flattened reconstruction view itself can be re-oriented(tilted), for example as shown in FIGS. 7A-7B.

Reference is now made to FIG. 3, which schematically represents aflattened image 40 of left atrium 2 anatomy including a superimposedactivation map, according to some embodiments of the present disclosure.

In some embodiments, a flattened reconstruction view of a tissue surfaceallows a user a simultaneous overview of features extending over a broadangular area. In FIG. 3, there is shown mapped to the LA anatomy anactivation map, wherein color indicates relative time after an impulsebegins that it reaches each particular region of the heart wall. The mapclearly identifies at a glance (e.g., with reference to time scale 41 inmilliseconds) that activity around pulmonary vein 10A is early enough tobe a potential triggering source for impulses (and, accordingly, ispotentially a preferred target for isolation by ablation). Moreover,since all PVs are shown simultaneously, it is relatively easy for anoperator to assess differences between and/or track changes in mapcharacteristics (e.g., as effects of ablation begin to appear in themap) at a range of widely separate target regions.

In some embodiments, use of superimposed (overlay) indications is usedto indicate another parameter, for example, directions of blood flow,which potentially indicates differences between blood vessels, valves,and other apertures in a heart chamber. For example in a left atrium,inward flow is from the pulmonary veins, outward flow from the mitralvalve, and flow is variable, low, and/or non-existent for the leftatrial appendage. Use of an overlay to indicate wall thickness is alsodescribed, for example, in relation to FIG. 11D. In some embodiments, aplurality of different overlay indications are available, (e.g., any ofthose described herein), and they can be turned on or off in anysuitable combination.

Reference is now made to FIGS. 8A-8B, which illustrate a source(un-flattened) reconstruction and a flattened reconstruction of a leftatrium 2 having a contour overlay, according to some embodiments of thepresent disclosure. Some features previously discussed are alsoindicated here, for example, pulmonary veins 10, probe 31, proximitymarkers 33, 34, mitral valve 12, and left atrial appendage 15.

The two different pairs of PVs 10 are each marked with surrounding innercontours 801, 803, and a series of outer contours 802, 804. The contoursare optionally spaced from each other at a constant distance along thesurface (for example, as shown). This potentially helps in emphasizing3-D structure, e.g., since contour lines will appear to be closertogether where the surface angles away from perpendicular to the viewingangle. Distortions of contours 804 near the top of the image (splayingto horizontally wider intervals) also help to indicate the “stretching”effect of distortions introduced during the flattening transformation.

Flattened Representations with Probe Position Indications

Reference is now made to FIG. 4, which schematically represents anavigational situation of a catheter probe 31 represented as moving withrespect to a flattened reconstruction view of a left atrium 2, accordingto some embodiments of the present disclosure. Reference is also made toFIGS. 5A-5B, which schematically represent indications of navigationaltarget, distance from a surface and/or direction of a catheter probemoving with respect to a flattened reconstruction view, according tosome embodiments of the present disclosure.

A full-surface view of a flattened reconstruction in particular, whethervariable or static, provides a potential advantage for reducing themental load on an operator working to move, monitor and/or otherwiseoperate (e.g., for treatment administration) a probe within anenvironment modeled by the flattened reconstruction.

In some embodiments, cues are provided which potentially help a userbetter understand the full 3-D position of a probe as it is shown movingwith reference to a flattened reconstruction view of a target tissue. Insome embodiments, the cues comprise a mark 33 which is projected onto aflattened reconstruction view of a surface of left atrium 2, dependingon the current position of probe 31. Optionally, mark 33 highlights aposition of a longitudinal axis extending through probe 31, at theregion where it intersects the atrial wall. As the probe gets closer tothe atrial wall (e.g., as in the movement between FIGS. 5A and 5B), theflattened reconstruction view shows mark 33 and probe 31 approachingeach other more closely. This method potentially gives visualdistinctiveness to different positions in depth when the catheter probe31 is angled significantly away from an axis extending orthogonal to thewall. Optionally, in some embodiments, the mark is also shade- orcolor-coded to indicate distance (e.g., becoming more intense as theprobe approaches the wall).

Optionally, the indicative change is a change in shape.

Another type of mark, in some embodiments, is illustrated by mark 35,which is optionally oriented to indicate a direction of movement and/ora direction of orientation of probe 31. Mark 35 is shown moving todifferent sides of mark 33 between FIGS. 5A and 5B; it should be notedthat it does not necessarily track the orientation of the probe itself.

Moreover, mark 35 is shown shorter in FIG. 5B than in FIG. 5A. Thedifference in length optionally tracks distance from the surface of theatrium 2, as an example of a shape change used to indicate probeposition in depth.

In some embodiments, lighting effects are used to help convey animpression of depth position to a user. For example, one or moresimulated lights are positioned to cast shadows from probe 31 onto thesurface of atrium 2. Optionally, this lighting is simulated in theflattened space defined by the transformed 3-D surface, as if it was anew space defined in Cartesian coordinates. Optionally or alternatively,the shading is rendered using the spatial configuration of the original3-D space, and shadows are rendered and transformed like other featuresof the atrium surface 2.

In some embodiments, there is only one light source, optionallysimulated as though emitting from the vantage point. Optionally, theshading of different portions of the surface is determined by the anglebetween the respective portion, and a line connecting the vantage pointto the center of the respective portion, for example as in Gouraudshading.

As a probe 31 is withdrawn further and further from the surface (towardan origin defined in the transformation, for example), it optionally isshown distorted as though being transformed directly from the original3-D space (i.e., using the same transform as is used to create theflattened reconstruction from the source reconstruction). Probe 31 mayappear to enlarge greatly, and/or begin to move more quickly across theimage for the same size movement, as if being held close to a “camera”.In some embodiments, one or more of these transformation effects issuppressed in some fashion. For example, a probe is optionally alwaysshown at the same size, about the same size, or at least not enlargedproportionally with its occupation of angular space with respect to acamera-like point of view. Potentially, this reduces a sense ofdisorientation that a dramatically magnifying probe might otherwisecause. For example, the probe is optionally plotted always at the samesize, hovering over the flattened reconstruction view surface positionwhich is nearest to it, and optionally with an angle appropriate toindicate its angle in the coordinates of the source reconstruction, inview of the selected rendering position in the flattened reconstruction.In some embodiments, rendering of the probe is simply suppressed forsome circumstances (e.g., at positions very near to the coordinateorigin), and allowed to re-enter the view at a well-defined position. Insome embodiments, it is the view itself that changes; e.g., thecoordinate origin is moved to keep it well away from the position of theprobe, or the view changes to a view of the source reconstruction from aflattened reconstruction view.

In some embodiments, the position of the probe tip is transformed fromthe source reconstruction to the flattened reconstruction by the sametransformation used for transforming the entire volume of the bodyportion, but the probe emerging from this position is always displayedstraight, and optionally of a fixed shape and/or size. The orientationof the straight probe display may be determined, in some embodiments, bythe coordinates in the flattened view of two points, e.g., one at thetip of the probe, and another near the tip of the probe.

A transformation origin and/or other projection parameters may also beadjusted, in some embodiments, even when the probe is moving near thetissue surface. For example, the origin is optionally moved closer totissue regions near the probe, potentially magnifying their appearance(e.g., allowing more detailed tracking) as they begin to subtend alarger angular size. Alternatively, the origin is optionally moved to aposition where it shows the current working region in the leastdistorted fashion available, which may be a more distant point of view.Either adjustment may produce a kind of lens effect (e.g., like a movingmagnifying glass), allowing the whole flattened reconstruction to remainbeing seen at once (e.g., to maintain a sense of orientation and/orcontext), while also providing the ability to selectively enhance theview in particular areas. Optionally, any parameter of flattening and/ordisplay is adjusted for a similar purpose, or another purpose assistingprocedure operations. For example, a flattened reconstruction view isoptionally tilted under manual user control and/or automatically inresponse to probe navigation events such as approaching apertures and/orcontact with tissue.

In some embodiments, there is not just one point of view (as defined,e.g., by a coordinate frame of reference and/or global curvature)defined even for a particular flattened reconstruction view; but ratherthe point of view is defined differently for the transformation ofdifferent positions in space. The selected point of view is optionallyvaried, for example, as a function of just θ and φ, as a function of r,as a function of all three variables, or in any other suitable fashion.The point of view definition is optionally varied continuously, whichcan help to alleviate jarring transitions, with the selection made fortransforming each region targeted to considerations particular to theregion; for example, one or more of the considerations described herein.For example, as a function of r from some origin point, the point ofview is optionally retreated in depth. This optionally reduces theproblem of probe “looming”, for example.

Reference is now made to FIGS. 6A-6B, which show the views of FIGS.1C-1D, respectively, together with indications of the position of acatheter probe 31. In both figures, probe 31 is indicated at a fixedsize. The position of probe 31 is determined, e.g., from a probetracking method such as electrical field and/or magnetic field basedtracking.

Also shown in each of FIGS. 6A-6B are surface proximity markers 33 and34. Proximity marker 33 is positioned to be centered on a point where acentral longitudinal axis of probe 31 intersects the source or flattenedreconstruction surfaces. This mark is potentially useful in indicatingwhere a catheter probe will make contact if advanced from its currentposition without additional steering control. Proximity marker 34 ispositioned to be centered on a point of the source or flattenedreconstruction surfaces closest to a distal tip of probe 31. If theflattened reconstruction view is oriented perpendicular to a lineconnecting it to the view's vantage point, this will generally putproximity marker 34 directly “under” the distal tip of probe 31, whileat offset view angles, the distance between probe tip and proximitymarker 34 becomes an indication of probe-surface distance. Proximitymarker 34 is potentially useful, for example, for indicating a potentialfor oblique surface contact and/or interference with movements of probe31. When the probe moves towards the wall, the two markers 33 and 34tend to approach each other, and when the probe is close to touching thewall, the markers may overlap each other.

Flattened Representations at Different Orientations

Reference is now made to FIGS. 7A-7B, which show the same flattenedreconstruction shown in FIGS. 1D and 6B, viewed at different tiltangles, according to some embodiments of the present disclosure. Probe31 and proximity markers 33, 34 are also shown in their visiblepositions.

In the angles shown, features of the flattened reconstruction can beviewed from the side and back. For example, more blood vessel branchesfrom pulmonary veins 10 are visible than from a substantially front-side(that is, interior-side) view. The surfaces of these vessels ramify asbranches exterior to (behind) more interior regions of the flattenedrepresentation. This illustrates in particular that in distinction, forexample, to a wide-angle projection image, there can be, for anyparticular (x,y) coordinate pair, a plurality of surface z positions. Itshould be noted in particular that positions of surfaces defining bloodvessels and their branches are mapped, in some embodiments, usingposition measurements obtained by movement of a catheter probe within abody lumen. This potentially reduces or removes a need for the use ofcontrast media in depicting blood vessel morphology.

It is also noted that the reconstruction is shown as everywhere closed;for example, blood vessels are shown “sealed off” at the limit of theirrepresentation in the flattened reconstruction. This is a featureinherited from the source reconstruction. There is no particularrequirement to avoid holes in producing the flattened reconstruction;e.g., holes in the source reconstruction may be considered to representsurfaces “at infinity”, or simply treated as missing data during thetransformation.

Flattened Representations of the Right Atrium

Reference is now made to FIGS. 11A-11D, which show different flattenedreconstruction views of a right atrium 3, according to some embodimentsof the present disclosure.

Particular features of a right atrium 3 shown in one or more of FIGS.11A-11D include apertures leading to superior vena cava 1102, inferiorvena cava 1104, and coronary sinus 1108 (CS). Also shown in one or moreof FIGS. 11A-11D is tricuspid valve 1110. In FIG. 11C, more details oftricuspid valve 1110 are particularly indicated, including septal,posterior, and anterior leaflets 1111, 1112, and 1113, respectively.FIG. 1C also indicates positions of the fossa ovalis 1106, Eustachianvalve 1105, and Thebesian valve 1109.

With particular reference to FIGS. 11A-11B, there are shown front(interior-side, endocardial view FIG. 11A) and back (exterior-side,epicardial view FIG. 11B) views of a flattened reconstruction of alumenal surface of right atrium 3. It should be understood that there isno particular limitation to these exact orientation. For example, aplurality of images from the flattened 3-D model may be produced fromany suitable viewing angle, wherein a first image is a view of theflattened 3-D model from a first direction, a second image is a view ofthe flattened 3-D model from a second direction, and the first andsecond images show different sides of a same surface portion.

Particularly noted is the position of the cavotricuspid isthmus 1114(CTI; located along the indicated dotted line). The CTI 1114 is ofinterest as a target for certain ablation procedures in the rightatrium, for example for the treatment of atrial flutter. In somepatients having a condition of atrial flutter, the condition iscontributed to by slow conduction along some directions through the CTI1114. By showing the CTI 1114 laid out in clear relation to nearbyfeatures, there is a potential advantage of a flattened reconstructionview for assisting a physician in locating and characterizing thisfeature for purposes of planning ablation, ablating, and/or verifyingablation along the CTI 1114.

FIG. 11C shows an example of ablations 120 applied over the CTI 1114. Itis noted that the particular flattened reconstruction layout of theinner lumenal surface of right atrium 3 places the tricuspid valve 1110at one border (the right), the superior vena cava 1102 at an oppositeborder (the left), and generally vertically centering the aggregate ofright atrium 3 apertures which extend in between. This arrangementpotentially serves to place discontinuities in the display at positionswhere they make little difference to decisions and operations involvedin navigating and/or treating the right atrium.

With respect to coronary sinus 1108: interventional cardiologists andelectrophysiology specialists are often challenged by a high degree ofvariability in the coronary venous anatomy during coronary sinuscannulation, left ventricular epicardial lead placement for cardiacresynchronization therapy (CRT), and/or intra-CS device deployment formitral valve repair. A precise and fully-automatic segmentation solutionfor detecting the coronary sinus would provide a potential advantage forsuch procedures.

Using field gradient-based remote imaging using an intracardialelectrode probe system the CS is among the features which may be rapidlydistinguished within a right atrium 3. The CS “bud” on the 3-Dreconstruction (source reconstruction) and its corresponding ‘dimple’ onthe (interior view) flattened reconstruction view may both be displayedwithin merely a few seconds after introducing a standardelectrophysiology catheter into the right atrium—even before physicallytouching the endocardial surface. Field gradient-based remote imagingalso potentially enables easily identifying and displaying of Thebesianvalve 1109, guarding the opening of the CS 1108, that often obstructscannulation of the CS 1108. The Thebesian valve 1109 anatomy is variableand rarely depicted in full by CT.

Once identified, the full course and anatomy of the CS 1108 can bedetermined by once or more inserting and pulling back theelectrophysiology catheter. This is a straightforward maneuver, requiresno contrast media or fluoroscopy, can potentially produce a highlyaccurate result.

FIG. 11D shows an (optionally color) overlay 1130 which indicates tissuethickness over a portion of the surface of right atrium 3. Inparticular, a region of maximal thickness 1107 is shown near theinferior vena cava 1104 (bar 1131 indicates how thicknesses map toshading of overlay 1130). In carrying out treatment ablations (theoptional positions of which are indicated to by spheres 1120), it is apotential advantage to know where tissue is thicker and thinner, forexample to allow adjustment of ablation parameters to ensure transmuralablation, and/or to avoid regions which are potentially too thick toeffectively ablate or too thin to safely ablate.

Flattened Representations from Field Gradient-based Remote Imaging ofthe Left Atrium

Reference is now made to FIG. 12, which presents a detailed flattenedreconstruction view of a left atrium based on data acquired using fieldgradient-based remote imaging, according to some embodiments of thepresent disclosure.

In some embodiments, data representing positions of a lumenal surface ofa body cavity are obtained using a remote electrical field imagingmethod, for example a method described in U.S. Provisional PatentApplication No. 62/546,775 entitled FIELD GRADIENT-BASED REMOTE IMAGING,and filed Aug. 17, 2017; the contents of which are incorporated hereinin their entirety.

FIG. 12 indicates potential levels of left atrium surface detail whichcan be obtained using this method, displayed using the flattenedreconstruction method.

Features shown already noted with respect to other figures hereininclude the pulmonary veins, here indicated specifically as the rightsuperior pulmonary vein 10D, right inferior pulmonary vein 10E, leftsuperior pulmonary vein 10F, and left inferior pulmonary vein 10G. Alsoshown are the left atrial appendage 15, trans-septal 17, and mitralvalve 12.

The clarity of the orifice of the left atrial appendage 15 ispotentially greater than typically seen in echocardiography, providing apotential advantage for the planning, guidance and/or verification ofleft atrial appendage occlusion procedures. Optionally, the flattenedreconstruction view is used to characterize the LAA orifice shape and/ordimensions.

Certain additional details can also be seen, including the left atrialappendage ridge 19. The clarity of the left atrial appendage ridge 19 ispotentially greater than typically seen in CT scans, providing apotential advantage for the planning, guidance and/or verification ofablations for arterial fibrillation, while saving exposure of thepatient and doctor to X-ray radiation. The morphology of ridge 19 isvariable among different patients (e.g., it can be more or lessprominent), and this can have a substantial impact on how ablationshould be performed—e.g., by its thickness (potentially requiringstronger ablation parameters, for example) and/or by its effect onablation line morphology (e.g., there may be a need to ablate on thesides of the ridge in order to get a continuous ablation line capable ofblocking electrical impulse transmission). Potentially, clearervisualization of the ridge or other surface irregularities helps aphysician to understand the results of a treatment (e.g., understand whyblockage is not initially achieved by an ablation treatment), and/or toplan new actions that will adjust the results.

Also shown are certain details of the mitral valve, including the threedivisions 1301, 1302, 1303 of the posterior mitral valve leaflet, andthe three divisions 1304, 1305, 1306 of the anterior mitral valveleaflet. This level of detail is seldom seen in CT scans, andillustrates a potential advantage of the method of field gradient-basedremote imaging, optionally in conjunction with a flattenedreconstruction view, for procedures such as mitral valve repair.

Systems for Flattened Representations of Curved Body Tissue Surfaces

Reference is now made to FIG. 13, which schematically represents asystem for production of a flattened reconstruction 1228 and/orflattened reconstruction view 1232, according to some embodiments of thepresent disclosure.

Block 1224 represents a source reconstruction, which is optionallyprovided and/or created based on data from a surface position sensingsource 1220 and/or 3-D image source 1222. The surface position sensingsource 1220 comprises, for example a catheter probe-based sensingsystem, using sensing of crossed electrical fields, self-generatedelectrical fields, local impedance characteristics, and/or anothermodality to generate data indicating positions of body tissue surfaces;for example by contact and/or proximity sensing together with probeposition sensing, by remote field imaging, and/or by another method. The3-D image source 1222 comprises, for example, an MRI image, CT image,radiography image, or another image type.

Transformation module 1226, in some embodiments, comprises a computerprocessor, processor instructions, and functionally associated computermemory, which are configured to transform source reconstruction 1224into flattened reconstruction 1228, for example as described in relationto FIGS. 1A-1G herein.

Rendering module 1226, in some embodiments, comprises a computerprocessor, processor instructions, and functionally associated computermemory, which are configured to produce a flattened reconstruction view1232 from flattened reconstruction 1228. For example, rendering module1226 is configured to render (e.g., using 3-D graphics processinghardware) a 2-D image from 3-D position data described by flattenedreconstruction 1228.

Examples of Global Curvatures and Flattening Results

Reference is now made to FIGS. 14A-14E, which schematically illustratedifferent 2-D examples of pre-flattening and post-flattening globalcurvatures and relief details, according to some embodiments of thepresent disclosure. The examples are provided in 2-D (that is, usingcurvatures of paths in two dimensions) to illustrate concepts describedherein in particular relation to curvatures of surfaces in threedimensions.

In FIG. 14A, curve 1401 represents a cross-section of a surface which isto be flattened. Circle 1402 represents a choice of the global curvature(e.g., a cross section of a sphere) which is to be flattened. In theparticular example shown, circle 1402 is chosen as a type of “best fit”circle. About as much area (analogous to volume, in the 3-D case) isenclosed by circle 1402 and not curve 1401 as is enclosed by curve 1401and not circle 1402. FIG. 14B represents a flattened version of FIG.14A. Line 1402A corresponds to circle 1402, with all the curvature ofthe circle removed. Cure 1401A represents relief details which remain incurve 1401 after removal of the global curvature. It is noted that anycircle concentric with circle 1402 (for example circle 1403) will alsobe flattened in this transformation (for example, as shown by circle1403A).

FIG. 14C represents a different flattened version of FIG. 14A, with someof the global curvature represented by circle 1402 remaining inflattened circle 1402B and flattened curve 1401B. Equivalently, adifferent choice of global curvature such as curve 1404 could be used asthe basis of flattening (and then flattened completely, for example line1404B) to result in a shape like that of 1401B.

The choice of global curvature is not limited to circles (or spheres in3-D), and a different choice can lead to a different residual result ofpreserved relief features. For example, ellipse 1404 of FIG. 14Dillustrates a different function which could be used to model a globalcurvature of path 1401. The resulting flattened curve (not shown) wouldsuppress relief features such as the pattern of long peaks 1410 andvalleys 1412 which superimposes on the shorter peaks 1412 and valleys1413 of FIG. 14B.

FIG. 14E shows another example in which a global curvature of anopen-sided curve 1405 is modeled by a parabola 1406 (in 3-D, the globalcurvature model could be a paraboloid, for example).

Considering circle 1402 (for example) as a reference shape, it may besaid that curve 1401 represents a shape isomorphic with relief details(like 1401A, 1402A, 1410, 1411, and 1412 of FIG. 14B, for example)superimposed upon the reference shape 1402 curving around a pointinterior to curve 1401 (which may be the center point or any otherinterior point). The relief details superimpose relative differences inradial offset from the interior point. The same language applies,changed as necessary for surfaces (rather than 2-D curves) representedin three dimensions by source 3-D models (which are the 3-D equivalentof a 2-D curve like curve 1401).

The word “isomorphic” in the foregoing paragraph should be understood tomean that the curve 1401 has the same shape as the reference curve addedtogether with the relief details (e.g., by offsetting). The terminologydefines a way of referring to the relief details represented in aflattened 3-D model, and of explaining their relationship to reliefdetails in a source 3-D model, without necessarily requiring that anexplicit decomposition into relief details and reference shape isactually performed.

Examples of Features Distinguishable on Flattening Results

Reference is now made to FIGS. 15A-15D, which schematically illustratefeatures visible on a flattened representation view of a right atrium(FIGS. 15A-15B) and left atrium (FIGS. 15C-15D), according to someembodiments of the present disclosure.

FIGS. 15A and 15C identify in outline features visible in correspondingpositions in the flattened representation views of FIGS. 15B and 15D,respectively.

Features identified in FIG. 15A include:

SVC superior vena cava IVC inferior vena cava EV Eustachian valve FOForamen ovalis CS Coronary sinus ThV Thebesian valve TV Tricuspid valveS, P, A Septal, posterior, and anterior leaflets of the tricuspid valveFeatures identified in FIG. 15C include:

TS Trans-septal puncture RSPV Right superior pulmonary vein RIPV Rightinferior pulmonary vein LSPV Left superior pulmonary vein LIPV Leftinferior pulmonary vein R Ridge of the left atrial appendage LAA Leftatrial appendage MV Mitral valve P1, P2, P3 First, second, and thirdposterior leaflet regions A1, A2, A3 First, second, and third anteriorleaflet regions

Reference is now made to FIG. 16A, which illustrates a triangularmeshing of the shape of a left atrium, according to some embodiments ofthe present disclosure. Reference is also made to FIGS. 16B-16E, whichillustrated different flattenings of the triangular meshing of FIG. 16A,according to some embodiments of the present disclosure.

The meshing of FIG. 16A comprises substantially equilateral andequal-sized triangles.

FIGS. 16B and 16D show internal (endocardial) and external (epicardial)views of the same flattened 3-D representation of the mesh of FIG. 16A.The flattening has been performed according to a rectangulartransformation, as described, for example, in relation to FIGS. 1C-1D.Triangles of the mesh are more nearly equilateral and uniform in sizenear the equatorial (central left-to-right) regions of the mesh. Nearerto the poles, (top and bottom), the triangles are stretched out, whichis indicative of the increasingly smaller circumference (and so, smallernumber of triangles) represented at each near-polar level. It may benoted in particular that horizontal lines extending from one edge of theflattened 3-D model to another edge of the flattened 3-D model distortdistances relative to the source 3-D model by substantially the sameamount through the linear region they extend across. The distribution ofdistortions may be changed in this as in other projection types bychanging the parameters of how the flattening is performed, e.g., wherediscontinuities are introduced, and what region is to be centered in theresulting flattened 3-D model.

FIGS. 16C and 16E also show internal (endocardial) and external(epicardial) views of the same flattened 3-D representation of the meshof FIG. 16A. The flattening has been performed according to anelliptical (Mollweide) transformation. The Mollweide projectioncorresponds to an equal-area, pseudocylindrical map projection whichtrades accuracy of angle and shape for accuracy of proportions in area.The triangles in these two images remain more nearly equal in area andshape over the extent of the image, though the angular distortionresults in the “up” and “down” directions (for example) tilting towardthe sides near the left and right edges of the reconstructions.

In either type of projection, there is also some change in triangle sizedue to the way that differences in depth cause differences in stretchingduring the “unwrapping”.

It should be understood that the types of flattening are not limited tothose shown, and may include, for example, the depth-preservingequivalent of any globe map projection method.

Examples of Continuous Updating of Images Using Flattening Results

Reference is now made to FIGS. 17A-17B, which each show a sequence ofimages produced from maps of various measurement phases (earlier tolater). The maps of later measurement phases are more refined, and showmore body lumen wall structure; based on a cumulative set ofintralumenal voltage measurements. In the images shown, measurementswere made using a method of electrical field measurement frommeasurement probe positions within the body lumen and remote from thebody lumen wall, for example as described in U.S. Provisional PatentApplication No. 62/546,775 entitled FIELD GRADIENT-BASED REMOTE IMAGINGand filed: Aug. 17, 2017; the contents of which are included herein byreference in their entirety. However, the general principle of updatingthe flattened images in response to new probe-measured data during aprocedure as it becomes available applies also to other forms of probemapping methods and/or measurements, for example methods described inU.S. Provisional Patent Application No. 62/445,433 entitled SYSTEMS ANDMETHODS FOR RECONSTRUCTION OF INTRA-BODY ELECTRICAL READINGS TOANATOMICAL STRUCTURE and filed Jan. 12, 2017, and also an InternationalPatent Application filed on the same date as this applicationPCT/M2018/050192, the contents of which are included herein by referencein their entirety.

Measurements used in FIGS. 17A-17B are from a patient. Each of the twoimage sequences will be described with reference to certain selectedfeatures shown, and their evolution throughout the sequence. Thesequences each proceed in time from left to right and from top to bottom(i.e., the upper-left image is the first image in the sequence, theimage below it is the fifth image in the sequence, and the image in thelower right is the sixteenth and last image in the sequence). Images aredisplayed as endocardial (that is, internal views of the internalsurface of the body lumen) panorama views, for example as described inrelation to FIGS. 1C-1D, herein. The imaged regions shown compriseinterior surfaces and connecting lumens, apertures, and/or cavities of aleft atrium.

In FIG. 17A, the initial image produced (e.g., using data obtained by anelectrode probe just after passage of the fossa ovalis from the rightatrium into the left atrium) is very low in overall detail resolution,and shows essentially just one putative lumen 1701. Lumen 1701 has beenautomatically assigned to the central position in the unwrappedpanoramic image, based on a weighting algorithm that seeks to put the“center of mass” of features distributed over the surface of the map atthe center of a panoramic image produced from the map.

As the number of available measurements increases, an apparent secondaperture 1702 appears in the images, offset from the first by about 180°(feature 1702 appears split, because it straddles the division made tosplay the atrium surface into a panoramic view). Later in the crossing(in the second row of four images), two relatively raised regions 1703,1704 also make an appearance. The raised regions, however, arepotentially better characterized as (initially) “feature free” regions,relative to the relative receded regions corresponding to directionswhich have been better measured so as to reveal features of the surface.All of these features move around slightly as the addition of newmeasurements results in a change in the center of mass (and thus achange in automatic flattening parameters used) of the featuresrepresented by the images of FIG. 17A.By the end of the third row, therecessed features identified are represented with relatively highresolution (sharper edges generally, for example, and resolution of twoholes within region 1701). However the detail available remains limitedby the restricted initial sampling region and probe orientations used.

Beginning in the fourth row, aperture feature 1702 now splits into twosub-features 1702A, 1702B. Region 1703 splits into two subregions 1703A,1703B. After revealing some new detail in area 1702B, the probe orientstoward the region of features 1701 and 1702A, making measurements thatfinally appear to resolve them as the left PVs and the right PVs,respectively. These veins are optionally treatment targets, e.g.,targets of a line ablation procedure intended to electrically isolatethe pulmonary veins so that they can no longer transmit impulses to theatrium which can result in uncoordinated contractions and/or atrialfibrillation. In the final image of the sequence, the measurement probehas returned to a position where it can measure the region of feature1702B, which now resolves as the apparent aperture leading to the mitralvalve (at far right of the darkened region indicated as feature 1702B),and another region (the left lobe of the darkened region 1702B) whichapparently indicates the LAA. Optionally, a user is presented with aninterface allowing manual tagging of features as their identities becomeapparent. Optionally, features are identified automatically based ontheir characteristics; individually and/or in comparison with otherresolved features.

Turning to FIG. 17B, two aperture-like features 1711, 1712, and oneraised area 1713 (really a “featureless” region) are initially visible.Further measurements result in refinement of this picture up to aboutthe second image of the second row. The region of feature 1712 (near thelower middle of the image) is selected as a first target for refinementby collection of additional data. This allows feature 1712 to becomeresolved into two distinct apertures 1712A, 1712B, with raised area 1713acquiring some feature texture and protruding in-between. By the lastimage of the third row, the measurement probe has also explored feature1711, which is revealed as partially merging with feature 1712B. Thefinal image (at lower right) reveals the right pulmonary veins withinregion 1712A (the two lobes of the darkening there apparentlycorresponding to the ostia of the superior and inferior right pulmonaryveins). The ostia of the left pulmonary veins are joined adjacent to oneanother (comprising feature 1712B) in a depression in common with theleft atrial appendage (corresponding to feature 1711), with a recessedridge in between. Raised region 1713 remains featureless extentextending between the left and right pulmonary vein ostia. Anotherdepression 1714 has also become apparent, apparently associated withfeatures of the mitral valve.

Further Flattening Transformations

Several methods for unfolding or flattening a model surface of an inner(or other) surface of a body have been described above. Described beloware further methods for unfolding a model surface of an inner surface ofa body that can be used in place of (or in addition to) any of themethods described above in conjunction with the described applications.In general, the surface of the body may be the outer surface of thatbody or the inner surface. For example, if the body is a heart chamber,the model surface may be a model of the outer surface of the heartchamber or of the inner surface of the heart chamber. An inner surfaceis referred to below by way of example.

In general terms, an unfolding transformation is a transformation thattransforms a closed 3-D model to an unfolded open 3-D model. Theunfolded model is also referred to as a flattened 3-D model. If anunfolding transformation is applied to an open 3-D model, the open 3-Dmodel becomes more open. For example, if the 3-D model being transformedmay be defined as an open smooth surface with relief details, theunfolded model may be defined as an open surface of lesser globalcurvature with corresponding relief details. Thus, an unfoldingtransformation is a transformation that transforms a model surface intoa (more) open surface, for example a surface having a smaller globalcurvature than the model surface. The model surface is a 3-D model ofthe inner surface of a body (also referred to as the source 3-D model),and the open surface is the unfolded model. If the model surfacecomprises relief details, the relief details may also be transformedinto relief details on the open surface. That is to say, the reliefdetails are maintained through the transformation and are not lostduring transformation, although they may be distorted. The unfoldedmodel or open surface therefore comprises the same or correspondingrelief details as 3-D model or the closed surface. The unfoldingtransformation may transform a 3-D model into an unfolded model, whereinthe unfolded model is an open surface. The unfolding transformation thustransform a model of a 3-D inner surface of a body into an unfolded 3-Dmodel of the inner surface. The method is particularly useful where theinner-surface of the body is a non-developable surface.

The 3-D model of an inner 3-D surface of a body may be defined by pointson a model surface, which models the inner surface. The unfoldingtransformation may thus transform points of the model to correspondingpoints of an unfolded model defining the unfolded model surface, andthus an unfolded model of the inner surface.

With reference to FIG. 18, a method of visualising a 3-D model of aninner 3-D surface of a body comprises a step of 1810 of obtaining 3-Dcartesian coordinates of points of the model. The model is defined bythe points and the points define a model surface that represents theinner surface of the body. The model surface may be a non-developablesurface, and the model surface may be a closed surface. In other words,the model surface may have two-dimensional curvature such that thesurface cannot be flattened without distorting respective distancesbetween points on the surface. The model may be obtained from signalsfrom a catheter 1920 as described below or may be provided on acomputer-readable storage medium or over a data connection forvisualisation. Coordinates of points used in the method described abovemay points that have been derived from the catheter signals to definethe model, or any other points defining the model or extracted from themodel.

The action of obtaining the 3-D model may comprise, in some embodiments,reading coordinates from a file, or receiving data from a digital memoryin any other way. In some embodiments, data indicative of thecoordinates of a model of the inner surface is obtained, and these dataare processed using methods discussed below to produce the unfoldedmodel.

At step 1820, an unfolding transformation is applied to the pointsdefining the model surface of the model. The unfolding transformationmay be applied to each point of the model and transforms the coordinatesof each point of the model to transformed 3-D coordinates or points. Thetransformed points define an unfolded model surface, that is an opensurface that represents an unfolded model of the inner surface of thebody. The unfolding transformation is carried out by a processor of acomputing device, for example a processor 1950 as described below.

At step 1830, a view of the unfolded model surface is displayed on adisplay or the unfolded model and/or view may be stored for laterdisplay. The view of the unfolded model may be displayed by a display1960 as described below with reference to FIG. 19, such as a videodisplay unit such us a liquid crystal display (LCD) or a cathode raytube (CRT). The view of the unfolded model may be a view of the pointson the unfolded model surface, wherein each point is displayed at itsrespective transformed coordinates, for example in the form a wire mesh,solid lit surface, polygons or splines defined by the points or usingany other suitable visualization technique.

To generate any view of the unfolded model at step 1830, in someembodiments, the coordinate system of the unfolded model relative to theviewing frame of reference may be determined. This defines a viewingdirection from which the unfolded model is viewed or in other wordsdefines an orientation of the unfolded model relative to the viewingframe of reference.

A reference cartesian coordinate system may be displayed together withthe view of the unfolded model. It is usually preferable to choose twocartesian planes that are perpendicular to each other, like the XZ andXY planes. The perpendicularity is not necessarily perfect, for example,the two planes may have between them angles other than 90°, for example,angles between 80° and 100°, or even between 60° and 120°. Additionallyto determining image planes, one may also determine the kind of shading,direction of the shading light, position of the shading light source,etc.

The method illustrated by FIG. 18 optionally comprises steps 1840, 1850and 1860 relating to displaying a view of a catheter position togetherwith view of the unfolded model surface. Steps 1840 to 1860 may becarried out at the same time as steps 1810 to 1830, or may be carriedout before or after steps 1810 to 1830.

At step 1840, coordinates for catheter points surrounded by the modelsurface are obtained. The catheter points define the position of acatheter, or more specifically, a distal end of a catheter, inside thebody. The catheter points may be a single point representing theposition of the catheter or a plurality of points representing theposition and orientation of the catheter inside the body. Thecoordinates of the catheter points may be obtained from a catheter 1920as described below or may be stored on a computer-readable storagemedium, as described above for the model points.

At step 1850, the unfolding transformation is applied to the coordinatesof the catheter points to obtain transformed coordinates for transformedcatheter points. The transformed catheter points define the position ofthe catheter with respect to the unfolded model surface. The transformedcatheter points may be indicative of the position of the catheter withrespect to the unfolded model. The position of the catheter with respectto the unfolded model may be indicative of the position of the catheterwith respect to the inner surface.

At step 1860, a view of the catheter at the transformed coordinates isdisplayed together with the view of the unfolded surface. The view ofthe catheter may comprise a marker indicative of the position of thecatheter at the transformed coordinates, wherein the marker is displayedtogether with the view of the unfolded surface to show the position ofthe catheter with reference to the unfolded surface. As an example, FIG.6B illustrates a view of the unfolded surface of a heart chamber 2together with a marker 31 indicating the position of a catheter insidethe heart chamber. The marker may be indicative of the orientation ofthe catheter inside the heart chamber. For example, the marker mayindicative the direction in which the distal end of the catheter ispointing. More specifically, other ways of displaying a catheter markerrelative to an unfolded surface are described above and are equallyapplicable here.

Steps 1840 to 1860 may be omitted or replaced by other steps. Forexample, the view of the unfolded model may or may not comprise anindication of the position of the catheter within the body at thetransformed coordinates.

Optionally the method further comprises a step of computing an updatedview of the unfolded model based on additional points of the model. Inmore detail, the method comprises obtaining additional points of themodel, wherein the additional points are additional points on a modelsurface modelling the model. The additional points of the model may beobtained from measurements taken inside the body, and the measurementsmay be taken by the catheter 1920 inside the body. The method comprisescomputing an updated unfolded model by applying the unfoldingtransformation to the additional points of the model to transform eachof the additional points of the model to a corresponding additionalpoint of the unfolded model. The unfolded model may comprise theoriginal points of the unfolded model and the additional points of theunfolded model. The unfolded model may be a completely updated unfoldedmodel, wherein the updated unfolded model only comprises the additionalpoints of the unfolded model and not the original points of the unfoldedmodel.

Optionally the method further comprises a step of obtaining coordinatesfor new catheter points defining a new position of the distal end of thecatheter inside the body. The unfolding transformation is applied to thenew catheter points and a view of the catheter at the new transformedcoordinates (the new transformed catheter points) is displayed togetherwith a view of the unfolded surface. The view of the catheter at the newtransformed coordinates may comprise the marker, wherein the marker ismoved from the transformed catheter points to the new transformedcatheter points. For example, moving the marker may involve making themarker disappear from the old position (the original transformedcatheter points) and making the marking appear at the new position (thenew transformed catheter points).

Optionally, the view of the unfolded model comprises a combination of acentral model modelling a portion of the surface of the heart chamber ina first rendering method, and a peripheral model modelling the rest ofthe heart chamber in a second rendering method, wherein the peripheralmodel is spread at the periphery of the central model. The methoddescribed above may further comprise the step of causing the display ofthe view of the unfolded model as a combination of the central model anda peripheral model.

In some embodiments, the method further comprises defining the firstportion of the surface of the heart chamber as a portion of the surfacelying at one side of a cutting surface and the rest of the surface ofthe heart chamber as that portion of the surface lying at the other sideof the cutting surface, wherein the cutting surface is defined as asurface going through a desired vantage point and perpendicularly to adesired viewing direction.

FIG. 19 illustrates a block diagram of one implementation of anapparatus 1910 configured to perform any one or more of themethodologies discussed herein. For example, the apparatus may beconfigured to carry out the method illustrated in FIG. 18. The apparatus1910 comprises an input module 1930 configured to receive informationindicative of the points of the model. The information may be any kindof data the represents the coordinates of the points of the model or maybe signals indicative of measurements taken inside a heart chamber. Theinformation may be stored at a separate storage medium coupled to theinput module. The information may be coordinates of the points of themodel or may be information indicative of the points of the model.

Optionally, the apparatus 1910 comprises or can be coupled to a catheter1920. The catheter may be configured to take measurements inside a heartchamber and may be coupled to the input module 1930 which receivessignals from the catheter, wherein the signals are indicative of themeasurements taken by the catheter inside the heart chamber. Themeasurements may be indicative of the structure of the inner surface ofthe heart chamber and may be indicative of the position of the catheterinside the heart chamber. Catheter 1920 may be designed for intra-bodynavigation; for example: an electrophysiology (EP) ablation catheter,and/or another ablation catheter (e.g., a chemical ablation or injectioncatheter). Catheter 1920 may comprise a plurality of physical electrodesand/or sensors (optionally, the electrodes serve as the sensors) locatedon a distal end portion of the catheter. The plurality of electrodesand/or sensors may be configured to take measurements such as electricalor magnetic measurements. The electrodes and/or sensors may beconfigured to sense the position of the catheter within a heart chamber,and may be able to sense the position of points on the inner surface ofthe heart chamber. The electrodes may be configured to communicate withthe processor. In some embodiments, a processor 1950 may receive input(e.g., from a user), indicative of the number of the electrodes and/orof the distances between them. In some embodiments, the distances areused for generating a 3-D model from electrical readings made byelectrodes of the catheter using the above-mentioned local scaling. Forexample, the user may provide a commercial name of the catheter probe(or the catheter) being used, and the at least one processor may beconfigured to associate each such commercial name with a number ofelectrodes and distances between them, e.g., by reading the data from apre-programmed lookup table.

In examples of implementations of the apparatus 1910, the input module1930 may be a processor configured to receive signals from the catheter1920 via electrical wires, or via a wireless means of transmitting thesignals. The input module may therefore comprise input terminals such assockets configured to receive electrical wires or may comprise awireless receiver for receiving the signals. Alternatively, the inputmodule 1930 may not have a processor and may instead comprise an inputterminal such as a socket for receiving wires or a wireless receiverthat is coupled to the converting module 1940 and/or processor 1950.

Embodiments of the present disclosure describe a way to transform acloud of electrical readings to a cloud of locations, and reconstructingthe location cloud into a 3-D model. The electrical readings arereceived by catheter 1920 electrodes when the catheter is inside theheart chamber. The catheter carries at least two electrodes (referred toas “sister electrodes”), the distance between them is known. Themeasurements made simultaneously be sister electrodes may be referred toas sister measurements, and the locations, to which sister measurementsare transformed, may be referred to as sister locations. To find atransform that transforms the measurements to locations in asatisfactory manner, a cost function is defined, and a transform thatminimizes this cost function is searched for. The cost function has atleast a local scaling term. The local scaling term is minimized byminimizing the difference (or ratio) between the distance between sisterelectrodes and the distance between sister locations. The modelsobtained from such a method may be even improved if the metrics thatdefine the distances are intrinsic to the structure of the heartchamber.

In some embodiments, the cost function may include two terms: the localscaling term and a coherence term. The coherence term is minimized whenmeasured values that are close to each other (under some metric) aretransformed to locations that are close to each other (under the same orother metric); and measured values that are far from each other aretransformed to locations that are far from each other.

The catheter may be configured to send signals based on the measurementsof the sensed position of the catheter or the sensed position of pointsof the surface of the heart chamber. Information based on the sensedposition of points on the surface of the heart chamber may be used todetermine coordinates of points on the model surface of the model of thesurface of the heart chamber.

Catheter 1920 may be coupled to the input module 1930, or alternativelyor additionally may be coupled to converting module 1940 and processor1950. The electrodes of the catheter may be configured to communicatewith at least one of the input module 1930, converting module 1940, andprocessor 1950. For example, the electrodes may send signals viaelectrical wires or via a wireless means for transmitting signals to therespective module or processor.

Catheter 1920 may be omitted from the apparatus of FIG. 19 and the inputmodule may be configured for receive information indicative of thepoints of the model from any other means that can send such information.

Apparatus 1910 further comprises a converting module 1940 configured toconvert the signals into coordinates of points defining a model surfacemodelling the model the inner surface of the heart chamber. Theconverting module may also be configured to convert signals intocoordinates for the position of the catheter inside the heart chamber.Converting module 1940 may be omitted from the apparatus 1910 if theinformation received by the input module comprises coordinates of pointsof the model and coordinates for the position of the catheter.Converting module 1940 may be coupled to input module 1930 such thatconverting module 1940 is configured to receive the signals from theinput module. Optionally, input module 1930 may be omitted and theconverting module may receive the signals indicative of measurementstaken by the catheter.

In examples of implementations of the apparatus 1910, the convertingmodule 1940 may be a processor configured to receive signals from theinput module 1930 and convert the signals into coordinates. Theconverting module may comprise input terminals such as socketsconfigured to receive electrical wires connecting the input module 1930and the converting module 1940, or may comprise a wireless receiver forreceiving the signals from the input module. Alternatively, the inputmodule 1930 may be omitted from the apparatus 1910 and the convertingmodule 1940 comprises a processor configured to convert signals intocoordinates, and input terminals configured to receive the signals fromthe catheter 1920.

Apparatus 1910 further comprises a processor 1950 configured to performany one or more of the methodologies discussed herein. The processor1950 may be configured to perform any one or more of the unfoldingtransformation methodologies discussed herein. The processor may beconfigured to receive coordinates of points from the converting module1940, or alternatively from the input module 1930, or alternatively fromthe catheter 1920. The processor 1950 may be configured to compute theunfolded model by applying the unfolded transformation to thecoordinates of the points of the model of the surface to obtaincoordinates of points of the unfolded model. The processor may carry outthe unfolding transformation in accordance with any of the unfoldingtransformations discussed herein for each point of the model,transforming the coordinates of each point of the model to transformedcoordinates. The transformed coordinates of each point of the modeldefine points on an unfolded model surface. The processor may also carryout the unfolding transformation in accordance with any of the unfoldingtransformations discussed herein for the coordinates for the position ofthe catheter inside the heart chamber. The processor may be configuredto cause a display of a view of the unfolded model by processing a viewof the points of the unfolded model surface, as well as the transformedcatheter points. The processor may be configured to cause a display ofthe view of the unfolded model by sending the transformed coordinates ofthe points of the unfolded model and the transformed coordinates of thecatheter points to a display unit.

In examples of implementations of the apparatus 1910, the processor 1950may be any type of computer processor configured to carry out theunfolding transformation on the coordinates of the points of the modeland the catheter. The processor 1950 may comprise input terminals suchas sockets configured to receive electrical wires connecting the inputmodule 1930 and/or the converting module 1940 to the processor, or maycomprise a wireless receiver for receiving the signals from the inputmodule and/or converting module. Alternatively, the input module 1930and converting module may be omitted from the apparatus 1910 and theprocessor 1950 comprises: a computer processor configured to convertsignals into coordinates and carry out the unfolding transformation onthe coordinates; and input terminals configured to receive the signalsfrom the catheter 1920.

The apparatus 1910 may further comprise a display 1960 for displaying aview of the unfolded model. Alternatively, the apparatus 1910 maycomprise an output for outputting a display signal to cause an externaldisplay to display a view of the model. Display 1960 may be configuredto receive information indicative of the view of the unfolded model fromprocessor 1950. The information may be the coordinates of the points ofthe unfolded model and coordinates of the transformed catheter points.Alternatively, display 1960 may receive information from the processor1960 indicative of a rendered image of the unfolded model. In examplesof implementations of the apparatus 1910, display 1960 may be a videodisplay unit such us a liquid crystal display (LCD) or a cathode raytube (CRT) and may comprise a screen such as a touch screen. Display1960 may comprise input terminals such as sockets configured to receiveelectrical wires connecting the display to processor 1950.

The view of the unfolded model displayed by display 1960 may be a viewof the points on the unfolded model surface, and may also comprise amarking at transformed catheter points, wherein the transformed catheterpoints are points of the unfolded model and the transformed coordinatesfor the position of the catheter inside the heart chamber. The markingat the transformed catheter points may be indicative of the positionand/or orientation of the distal end of the catheter.

Optionally, the apparatus further comprises a user interface configuredto receive display instructions from a user. A view of the unfoldedmodel may be displayed by the apparatus in accordance with the displayinstructions.

As an example, the display instructions may comprise instructions todisplay an icon indicative of the viewing direction, i.e. the directionat which the unfolded model is viewed. The apparatus may then display aview of the unfolded model together with this icon. As a furtherexample, the display instructions may comprise instructions to display aview of the unfolded model at a user-defined orientation. The apparatusmay then display a view of the unfolded model at this orientation. Ingeneral terms, the user interface may receive an indication of anorientation of the unfolded model, and the display may display the viewof the unfolded model at the orientation indicated via the userinterface.

The user interface may allow a user to change the origin and/or theviewing direction by dragging a mouse or manipulating another user inputdevice, such as a stylus, slider, knob or button, which may beimplemented as physical features or on-screen. For example, clicking themouse on the origin and dragging may move the origin, while clicking themouse away from the origin and dragging it may change the viewing angle.

As yet a further example, the display instructions may compriseinstructions to display a view of the model with a user-defined degreeof unfolding. The display instructions may comprise the value of anunfolding factor α which may be selected by the user. In other words,the user can indicate to the processor 1950 a desired degree ofunfolding. The indication may be, for example, by entering a value forthe unfolding parameter, or by adjusting an adjustable input elementwith an adjustable position or orientation. For example, an off-screeninput element may be a knob that can be switched between two or morepositions, each corresponding to a particular value of the unfoldingparameter. In another example, an on-screen input element may be aslider that can be slid between two or more values of the unfoldingparameter, a button or a knob, or any other adjustable indication means.In some embodiments, the partly unfolded view changes to reflect themomentary value of the unfolding parameter, as the user changes theindication, for example, by sliding the slide. In some embodiments, themodel unfolds in front of the eyes of the user, providing further helpin understanding the relationship between the folded and unfolded view.In other words, the apparatus may be configured to display a view of theunfolded model with an intermediate degree of unfolding as the userchanges the unfolding factor from an initial value to a final desiredvalue. In some embodiments, the user may control the pace at which theunfolding is demonstrated, stop (and then opt to continue) the unfoldingat any point he wishes, The apparatus may then display the view of theunfolded model in accordance with the unfolding factor, α. The unfoldingfactor may be specified by the user by entering a numerical value. Theunfolding factor α is explained below.

As yet a further example, the display instructions may compriseinstructions to display a second view of the unfolded model at the sametime as displaying a first view of the unfolded model. The displayinstructions may further comprise instructions to display the secondview of the unfolded model at a user-defined orientation. In generalterms, the user interface may receive an indication of an orientation ofthe unfolded model, and the display may display the second view of theunfolded model at the orientation indicated via the user interface.

The orientation of the second view of the unfolded model may bedifferent to the orientation of the first view. For example, thedirections from which the first and second model are viewed may be setto be transverse to each other, for example defining an acute angle ofbetween 60 and 90 degrees, more specifically between 70 and 90 or 80 and90 degrees. In some embodiments, the two viewing directions may beorthogonal to each other. By providing views that differ significantlyin orientation, it will be easier to judge distances and orientations ofan object such as a catheter or catheter tip displayed together with themodel relative to the model surface, since a distance that will resultin a shallow projection or obscured view in one of the views may beclearly visible in the other one of the views.

In one example, a plurality of views of the unfolded model may bedisplayed at a plurality of different orientations, wherein each view ofthe plurality of views is displayed sequentially. In other words, isview of the plurality of views is displayed one-after the other so as toprovide the effect of continuous movement of the view of the unfoldedmodel.

In another example a plurality of views of the unfolded model may bedisplayed simultaneously, wherein each view is indicative of a differentdegree of unfolding.

With reference to FIG. 20, an embodiment of an unfolding transformationmethod in accordance with step 1820 and 1850 of FIG. 18 and, forexample, as carried out by processor 1950 of FIG. 19 comprises a step of2010 of obtaining polar coordinates of the points on the model surfacemodelling the inner surface. In some embodiments, the points on themodel surface are provided in cartesian form and step 2010 may compriseconverting cartesian coordinates of the points of the model to polarcoordinates. For example, step 2010 may include using conventionaltransformations from cartesian to polar coordinates. Each point of themodel is then defined by polar coordinates, comprising an azimuthal,inclination, and radial coordinate. The polar coordinates are definedwith respect to an origin, such as a reference point within a volumesurrounded by the model surface. The azimuthal and inclinationcoordinates of each point of the model may be defined with respect to afirst axis and a second axis extending from the reference pointperpendicular to one another that together define a reference plane thatis perpendicular to the second axes and within which the first axislies. Specifically, the azimuth coordinate is defined as the anglebetween the first axes and the projection onto the reference plane ofthe model point line that extends from the reference point and throughthat point of the model. The inclination coordinate is defined as theangle between the model point line and the projection of the model pointline onto the reference plane. The radial coordinate of each point maybe defined as the distance between the origin and that point.

At step 2020, the azimuthal and inclination coordinates of each point ofthe model are reduced by multiplying each coordinate by an unfoldingfactor α that is positive and less than unity. The multiplied azimuthaland inclination coordinates of each point are the transformed azimuthaland inclination coordinates which represent the azimuthal andinclination coordinates of a corresponding point of the unfolded model.In other words, the azimuthal and inclination coordinate of each pointof the unfolded model equates to the azimuthal and inclinationcoordinate of the corresponding point of the 3-D model multiplied by theunfolding factor α. The effect of the multiplication with a, in generalterms, can be understood to move the points on the model surfacesangularly towards a line along the first axis and extending fromreference point. This line can be characterized as the line about whichthe model is unfolded.

The unfolding factor a may be considered to indicate a degree ofunfolding. In other words, a minimum value of a may signify a maximumdegree of unfolding. When α is smaller, each point of the modelundergoes a greater angular displacement and thus moves a greaterangular distance towards the first axis.

Alternatively, the azimuth and/or inclination coordinates may be reducedin a different manner, for example, by subtracting a value, or by anyother means that results in a reduction of the azimuth and/orinclination angle of each coordinate and in particular in angularmovement of the model points as described above.

In more general terms the effect of reducing the angles as describedmoves the points on the model surface closer together. Since the angularcoordinates of each point of the model are reduced, this means that theazimuth and inclination angles between each point of the model are alsoreduced, thus reducing the arc length along the model surface betweeneach point and thus moving the points closer together.

At step 2030, the radial coordinate of each point of the model isincreased so as to increase the global curvature of the unfolded modelsurface, in comparison to that of the model surface. In someembodiments, the increase in the radial coordinate of each point dependson the unfolding factor α. For example, a value depending on a may beadded to the radial coordinate of each point. Generally, the added valuemay depend inversely on a. In some embodiments, the overall area of themodel (or some other characteristic parameter of the model) staysunchanged in that the addition to the radial coordinates compensates forthe decrease in the angular coordinates so the surface area or othercharacteristic parameter of the model does not change considerably, ordoes not change at all. For example, the radial coordinate may beincreased by adding to the radial coordinate an amount inverselyproportional to the unfolding factor α. In some embodiments, the amountadded to the radial coordinate of each point of the model may equates tothe product of a value β and the difference between the inverse of theunfolding factor α and unity. The value β is indicative of the size of anotional closed surface centred on the reference point and surrounded bythe points on the model surface. Optionally, the notional closed surfaceis spherical and β is the radius of the notional closed surface ornotional sphere. The increased radial coordinate of each point is thetransformed radial coordinate which represents the radial coordinate ofa corresponding point of the unfolded model. In other words, the radialcoordinate of each point of the unfolded model equates to the radialcoordinate of the corresponding point of the 3-D model increased by anamount β(1/α−1).

In more general terms, the effect of increasing the radial coordinate asdescribed is to move the points on the model surface radially outward,thus reducing a curvature of the resulting surface and spreading thepoints apart by increasing the arc length between each point of thesurface. It will therefore be appreciated that any manipulation of theradial coordinate that achieves this effect may be used instead. Theincrease in radial coordinate thus results in an increase in arc lengthalong the model surface between each point and may compensate for thereduction in arc length between each point caused at step 2020 byreducing the angular and radial coordinates. Thus, the increase inradial coordinate can preserve distances between points of the modelwhen they undergo the unfolding transformation to become points of theunfolded model. It must, however, be noted that the arc length referredto above are along “longitudes” between “poles” where the first axisintersects the notional sphere. FIGS. 22A-22C discussed below show onesuch “longitude” circle and the effect of the transformation on pointson such a circle. It will be understood that arcs along any such circlethat is obtained by rotation about the first axis from the illustratedcircle behave in this way under the transformations, but that arcsacross such “longitudes” or circles, for example along “latitudes” maybe distorted by the transformation. Step 2030 may be performed before,after or at the same time as step 2020, since each of steps 2020 and2030 transform independent coordinates and so the transformation of theradial coordinate does not affect the transformation of the azimuth orinclination coordinates, and vice versa.

The steps of reducing the angular coordinates and increasing the radialcoordinates of each point has the effect of transforming a notionalclosed surface centred on the reference point and surrounded by themodel surface into a notional open surface. Points on the notionalclosed surface are transformed into points on the notional open surfaceby the transformations of 2020 and 2030. The radial increase 2030 ofeach point on the notional closed surface

$\delta = {\beta\left( {\frac{1}{\alpha} - 1} \right)}$

causes the arc length between points on the notional closed surface tobe persevered in face of the angular displacement 2020 of those points.Thus these transformation steps have the effect of causing the arclength between transformed points on the notional open surface to be thesame as the arc length between corresponding points on the notionalclosed surface. In some embodiments, the transformation therefore islength preserving along “latitudes” for points on the notional sphere ofradius β and similarly close to length preserving along “latitudes” forpoints close to that notional sphere.

The first and second axis defining the azimuth and inclinationcoordinates of each point of the model extend from the reference pointand pass through the notional closed surface at respective first andsecond surface reference points.

The steps of reducing the angular coordinates and increasing the radialcoordinates of each point of the model to transform the points of themodel to points of the unfolded model, in some embodiments, has theeffect of transforming a model surface into an unfolded model surface,such that a normal distance between each point on the model surface andthe notional closed surface is substantially equal to a normal distancebetween a corresponding point on the unfolded model surface and thenotional open surface.

As would be appreciated by a person skilled in the art, the notionalclosed surface and the notional open surface do not need to be definedin terms of actual coordinates, but are instead used here notionally toillustrate the effect of the unfolding transformation on the points ofthe model. Similarly, the first and second surface reference points donot need to be defined in terms of coordinates but can be defined as thepoints at which the first and second axes pass through the notionalclosed surface respectively, and can be defined as a first and secondnotional surface reference points.

At step 2040, the transformed azimuthal, inclination and radialcoordinates which represent the coordinates of the unfolded model areconverted to cartesian coordinates using conventional transformationsfrom polar to cartesian coordinates. This may be useful when usingrendering engines that work in cartesian coordinates but may be omittedif points are rendered directly in polar coordinates, for example. Ingeneral terms, therefore, step 2040 is optional.

The increase in the radial coordinate of each point of the model mayhave the effect of causing the resulting transformed points of theunfolded model to have a third (Z) coordinate far away from the origin(the reference point). The resulting view of the unfolded model maytherefore appear far away from the origin and thus smaller whendisplayed. In order to negate this, optionally, at step 2050, the Zcoordinate of each point of the unfolded model is transformed bysubtracting from the Z coordinate an amount equivalent to the increasein the radial coordinate defined in step 2030. For example, inembodiments where the radial coordinate is increase by addition ofβ(1/α−1), the Z coordinate of each point of the unfolded model may bereduced by an amount β(1/α−1).

The unfolding transformation method of FIG. 20 can equally be appliedusing analogous transformations to points of the model defined incartesian coordinates. In this case, step 2010 may be omitted or obtaincartesian coordinates of points of the model if the points of the modelare not already defined in cartesian coordinates. Steps 2020 and 2030may be replaced with corresponding analogous transformation steps forperforming equivalent transformation movements of the model points incartesian coordinates. In this case, step 2040 is omitted since thetransformed coordinates of the points of the unfolded model remaindefined in cartesian coordinates.

With reference to FIG. 21, another unfolding transformation method inaccordance with step 1820 and 1850 of FIG. 18 and, for example, ascarried out by processor 1950 of FIG. 19 comprises a step of 2110 ofobtaining polar coordinates of the points on the model surface modellingthe surface. Obtaining a representation of the points of the model inpolar coordinates may comprise transforming the coordinates of thepoints of the model into polar coordinates using conventionaltransformations to polar coordinates.

Step 2110 may comprise converting cartesian coordinates of the points ofthe model to polar coordinates using conventional transformations fromcartesian to polar coordinates. Each point of the model may then bedefined by polar coordinates, comprising an azimuthal, inclination, andradial coordinate. The polar coordinates are defined with respect to anorigin, such as a reference point within a volume surrounded by themodel surface. The azimuthal and inclination coordinates of each pointof the model may be defined with respect to a first axis and a secondaxis extending from the reference point. Specifically, the azimuthal andinclination coordinates of each point may be defined in the same way asdescribed with reference to FIG. 20.

At step 2120, the azimuthal and inclination coordinates of each point ofthe model are transformed by applying a cartographic projectiontransformation to transform the azimuth and inclination coordinates ofeach point of the model to obtain transformed x and y cartesiancoordinates. The cartographic projection may be a Mollweide projection,as described by Wolfram MathWorld™ athttp://mathworld(dot)wolfram(dot)com/MollweideProjection(dot)html, or aPlate Carrée projection, or any other kind of projection that transformsazimuthal and inclination coordinates to two-dimensional cartesiancoordinates. As would be understood by a person skilled in the art, acartographic projection transforms 2D coordinates into transformed 2Dcoordinates. Therefore, the cartographic projection does not affect theradial coordinate of the points of the model.

At step 2130, the transformed x and y cartesian coordinates of eachpoint of the model are reduced by multiplying each coordinate by theunfolding factor α that is positive and less than unity. This stepcauses analogous movement of the points as step 2020 described above andthe same considerations as to more generalized point movement apply.

At step 2140, the transformed and reduced x and y coordinates of eachpoint of the model are transformed back to azimuthal and inclinationcoordinates by applying the inverse function of the cartographicprojection. The inverse cartographic projection transforms thetransformed, reduced x and y coordinates of each point of the model toreduced azimuthal and inclination coordinates which represent theazimuthal and inclination coordinates of a corresponding point of theunfolded model. In other words, the azimuthal and inclination coordinateof each point of the unfolded model equates to the azimuthal andinclination coordinate of the corresponding point of the 3-D model whentransformed to cartesian coordinates using a cartographic projection,reduced by multiplication by a, and transformed back to polarcoordinates using the inverse of the cartographic projection. Theinverse cartographic projection does not affect the radial coordinate ofthe points of the model.

At step 2150, in some embodiments. the radial coordinate of each pointof the model is increased by adding to the radial coordinate an amountinversely proportional to the unfolding factor α. The amount added tothe radial coordinate of each point of the model equates to the productof a value β and the difference between the inverse of the unfoldingfactor α and unity. The value β is indicative of the size of a notionalclosed surface centred on the reference point and surrounded by thepoints on the model surface. Optionally, the notional closed surface isspherical and β is the radius of the notional closed surface or notionalsphere as described above. As described above, this radial movementcauses the points to move radially outwards and apart from each other inmore general terms, and the same considerations as for step 2030 apply.

The increased radial coordinate of each point is the transformed radialcoordinate which represents the radial coordinate of a correspondingpoint of the unfolded model. In other words, the radial coordinate ofeach point of the unfolded model equates to the radial coordinate of thecorresponding point of the 3-D model increased by an amount β(1/α−1).Since the transformations in steps 2120 and 2140 do not affect theradial coordinate of the points of the model, the transformation to theradial coordinate of each point of the model at step 2150 can occur atbefore, after, or at the same time as any of steps 2120 to 2140.

Similar to the method discussed above with reference to FIG. 20, thesteps of reducing the angular coordinates and increasing the radialcoordinates of each point has the effect of transforming the notionalclosed surface centred on the reference point and surrounded by themodel surface into a notional open surface. The radial increase 2150 ofeach point on the notional closed surface

$\beta\left( {\frac{1}{\alpha} - 1} \right)$

causes the arc length between points on the notional closed surface tobe persevered in face of the angular displacement (caused by steps 2120to 2140) of those points. Thus these transformation steps have theeffect of causing the arc length between transformed points on thenotional open surface to be the same as the arc length betweencorresponding points on the notional closed surface.

Also similar to the method discussed above with reference to FIG. 20,the steps of reducing the angular coordinates and increasing the radialcoordinates of each point of the model to transform the points of themodel to points of the unfolded model has the effect of transforming amodel surface into an unfolded model surface, such that a normaldistance between each point on the model surface and the notional closedsurface is substantially equal to a normal distance between acorresponding point on the unfolded model surface and the notional opensurface.

At step 2160, the transformed azimuthal, inclination and radialcoordinates which represent the coordinates of the unfolded model areconverted to cartesian coordinates using conventional transformationsfrom polar to cartesian coordinates. As for step 2040, this is optional.

The increase in the radial coordinate of each point of the model mayhave the effect of causing the resulting transformed points of theunfolded model to have a third (Z) coordinate far away from the origin(the reference point). The resulting view of the unfolded model maytherefore appear far away from the origin and thus smaller whendisplayed. In order to negate this, optionally, at step 2170, the Zcoordinate of each point of the unfolded model is transformed bysubtracting from the Z coordinate an amount equivalent to the increasein the radial coordinate defined in step 2150. In other words, the Zcoordinate of each point of the unfolded model may be reduced by anamount β(1/α−1).

Generally, it can be seen that step 2120, 2130 and 2140 correspond withstep 2120 described above and that step 2150 corresponds with step 2030and step 2160 corresponds with step 2040, so that the discussion abovein relation to FIG. 20 applies, mutatis mutandis, to the discussion ofFIG. 21.

The unfolding transformation of FIGS. 20 and 21 can equally be appliedto catheter points instead of or in addition to points of the model,wherein the catheter points are coordinates of the position of thecatheter.

FIGS. 22A-22C illustrate a schematic example of the unfoldingtransformation illustrated in FIG. 20 for points of the model defined inpolar coordinates. The unfolding transformation illustrated in thesefigures represents a “partial” unfolding of closed model surface 2280 inFIG. 22A to partially unfolded model surface 2280′ in FIG. 22B andpartially unfolded model surface 2280″ in FIG. 22C. In this case, apartially unfolded model surface corresponds to an intermediate value ofthe unfolding factor, α. In other words, for a partially unfolded model,the unfolding factor α is a value in between the minimum and maximumvalue, and thus the degree of unfolding is between a minimum and amaximum. More generally, a partially unfolded model is a model that maybe described as an open curved surface, or an open surface with a finitecurvature, while a folded model may be described as a closed curvedsurface, and fully unfolded model may be described as an open, flatsurface. That is, a fully unfolded model may be a surface withzero-curvature.

In the 2-D representation illustrated in FIGS. 22A-C, the circle 2280representing the model surface represents a longitude circle asdiscussed above. Arc lengths between points along this longitude circle2280 are preserved as the unfolding transformation increases the radialcoordinate and reduces the azimuth coordinates of the points of themodel onto points of longitude circle 2280′ or 2280″. As an example,these figures illustrate the unfolding transformation for the azimuthaland radial coordinates of each point of the model. The skilled personwould appreciate that this unfolding can be extended to a 3-D model,wherein the inclination coordinate can be transformed in a similarmanner. As would be appreciated by the skilled person, this unfoldingtransformation can equally be applied using analogous transformations topoints of the model defined in cartesian coordinates, or any otherrepresentation.

With reference to FIG. 22A, a notional closed surface 2230 (dashed) iscentred on a reference point 2240. Notional closed surface 2230 does notneed to be defined in terms of coordinates of points on the notionalclosed surface. Instead, notional closed surface is only used to aid inunderstanding the effect of the unfolding transformation. In otherwords, notional closed surface 2230 is “notional” since it does notnecessarily actually exist as part of an unfolding transformation, butis only used herein to explain the effect of the unfoldingtransformation.

In the example illustrated, notional closed surface 2230 is a sphericalshape (circular in 2-D), however notional closed surface 2230 may beanother other type of closed surface shape, such as an ellipsoid or anyarbitrary closed surface. The centre 2240 of the notional closed surface(the position of the reference point surrounded by the notional closedsurface) is defined as the average of the coordinates of all points thatlie on the surface of the notional closed surface. In reference to FIGS.22A-22C, notional closed surface 2230 is hereinafter referred to asnotional sphere 2230.

A first surface reference point 2220 lies on the surface of the notionalsphere and a first axis 2210 extends from the reference point 2240 andthrough first surface reference point 2220. For consideration of the 3-Drepresentation, the second axis would extend from the reference point2240 in a direction perpendicular to the first axis. Points 2270 and2275 represent points of the model that lie in the plane of the Figureand on a model surface 2280 modelling the inner surface of a body andsurrounding the notional sphere 2230. For simplicity, model surface 2280in FIG. 22A has been illustrated as a regular, circular shape. However,model surface 2280 may be any arbitrary 3-D surface surroundingreference point 2240, and points 2270 and 2275 may be at any point onthe model surface. Normal distances 2260 and 2265 between the notionalopen surface 2290 and points 2270 and 2275 respectively may havedifferent values. Also, while first surface reference point 2220 is onthe angle bisector bisecting the angle between points 2270, 2240, and2275, so that the angles A and B are equal, this is not necessarily so,and first axis 2210 may extending from the reference point in anydirection in the plane of the Figure such that first surface referencepoint 2220 may be at any place along notional sphere 2230 where thefirst axis passes through the notional sphere.

The points 2270 and 2275 lie outside of the notional sphere and haverespective normal distances 2260 and 2265 between the points and thenotional sphere. Normal distances 2260 and 2265 are the distancesbetween the notional sphere 2230 and points 2270 and 2275, when measuredalong a line extending between the reference point 2240 and eachrespective point 2270 and 2275. Distances 2250 and 2255 are the radialdistances between the reference point 2240 and the surface of thenotional sphere. Since notional sphere 2230 is not part of the unfoldedtransformation and is only used to illustrate the effect of theunfolding transformation, normal distances 2260 and 2265, and distances2250 and 2255 are also only used to illustrate the effect of theunfolding transformation and are not necessarily defined as part of theunfolding transformation itself but rather characterize unfoldingtransformations of some disclosed embodiments. Distances 2250 and 2255are measured along the line extending between the reference point andpoints of the model 2270 and 2275 respectively. The radial coordinate ofpoints 2270 and 2275 are defined as the sum of 2250 and 2260, and 2255and 2265 respectively. Angles A and B are the angles made between thefirst axis 2210 and lines 2250 and 2260 respectively. The azimuthal orinclination coordinate of points 2270 and 2275 may be defined as anglesA and B respectively. FIG. 22A illustrates a model prior to an unfoldingtransformation being applied to the points 2270 and 2275.

FIG. 22B illustrates the points 2270 and 2275 following an unfoldingtransformation. Points 2270 and 2275 have been transformed by theunfolding transformation and are now points of the unfolded model on anunfolded surface 2280′. The unfolding transformation has the effect oftransforming notional sphere 2230 into notional open surface 2290.Notional sphere 2230 is a notional closed surface, which has beentransformed to notional open surface 2290 using the unfoldingtransformation. Notional open surface 2290 has a larger radius thannotional sphere 2230, since the radius of the notional sphere isincreased by the unfolding transformation by adding an amount

$\delta \propto \left( {\frac{1}{\alpha} - 1} \right)$

such that arc lengths between points on the notional sphere arepreserved during the transformation. Thus, the length of the arc ofnotional open surface 2290 between lines 2250 and 2255 (through point2220) is the same as the length of the arc of notional sphere 2230between same lines. Optionally, the increase is addition of an amount

${\delta = {\beta\left( {\frac{1}{\alpha} - 1} \right)}},$

wherein β is indicative of the radius of the notional sphere 2230. Thenotional sphere 2230 is shown in FIG. 22B to illustrate the increase inradius as the notional sphere undergoes the unfolding transformation andis transformed to the notional open surface 2290.The unfolding transformation illustrated in FIG. 22B has been carriedout using unfolding factor α, where α is positive and less than unity.Points 2270 and 2275 have been angularly displaced in a directiontowards first axis 2210 by multiplying angles A and B respectively by α,thus reducing the angles and causing an angular displacement of points2270 and 2275 towards first axis 2210. In other words, the azimuthal orinclination coordinate of the points 2270 and 2275 have been reduced.The radial coordinate of points 2270 and 2275 have been increased byadding δ to distances 2250 and 2255. This way, radius 2250, 2255 of thenotional open surface 2290 has been increased, whilst the normaldistances 2260 and 2265 between points 2270 and 2275 respectively andthe notional open surface 2290 remains unchanged, i.e., the same as inFIG. 22A. In other words, the unfolding transformation has the effect oftransforming notional sphere 2230 into notional open surface 2290 suchthat normal distances 2260 and 2265 between points 2270 and 2275 andcorresponding points on the notional open surface are substantiallyequal. Here, substantially equal is intended to mean that the respectivenormal distances are equal to within tolerances, such as rounding errorsor other systematic errors that may arise within the implementation ofthe unfolding transformation.As an example, the 3-D model may be a model of an inner surface of aheart chamber, and the model may include relief details showing, forexample, a “deep hole” that models a blood vessel connected to the heartchamber, and may also include relief details showing a “ridge” in thesurface of the heart chamber. It will be appreciated that a point on themodel surface representing the deep hole may have a large normaldistance to a notional sphere defined within the surface of the heartchamber, and equally, a point on the model surface representing theridge may have a small normal distance to the notional sphere.Therefore, when the unfolding transformation is applied, thecorresponding point for the deep hole on the unfolded model will have anormal distance to a notional open surface 2290 which is substantiallythe same as the normal distance between the point on the model surfacerepresenting the deep hole and the notional sphere defined within thesurface of the heart chamber. Equally, the corresponding point for theridge on the unfolded model will have substantially the same respectivenormal distance to a notional open surface. This illustrates that theunfolded model contains the same relief details as the 3-D model of thesurface.

FIG. 22C also illustrates points 2270 and 2275 following an unfoldingtransformation in the same manner as FIG. 22B, but with a differentvalue of the unfolding factor α. More specifically, the unfolding factorα is smaller for FIG. 22C compared to FIG. 22B, indicating a largerdegree of unfolding. The reduction in angles A and B is larger in FIG.22C compared to FIG. 22B since A and B are multiplied by smallerunfolding factor α. In other words, the reduction of the azimuthal orinclination coordinates of points 2270 and 2275 is larger. Therefore,the angular displacement of points 2270 and 2275 towards first axis 2210is larger.

Equally, the increase in the radial coordinate (due to the increase inthe radius 2250 or 2255 of the notional open surface 2290) is larger inFIG. 22C compared to 22B, since the increase is inversely proportionalto α.Following the angular displacement and increase in radial coordinates,points 2270 and 2275 illustrated in FIG. 22C are points of the unfoldedmodel on the unfolded model surface 2280″. Unfolded model surface 2280′of FIG. 22C has a larger radius, i.e. less curvature, than unfoldedsurface 2280′ of FIG. 22B. Unfolded surface 2280″ of FIG. 22C thereforehas a larger degree of unfolding since the unfolded surface 2280″ ofFIG. 22C is closer to a fully unfolded (flat, zero curvature) surface.

As would be understood by the skilled person, the angular and radialmovement of points 2270 and 2275, shown in FIGS. 22B and 22C withreference to the original positions shown in FIG. 22A, may equally beimplemented using corresponding transformations for other cartesiancoordinates systems (e.g., a Cartesian coordinate system) if points 2270and 2275 are defined in cartesian coordinates this other coordinatesystem.

FIGS. 22A-22C are merely illustrative examples of an unfolding processin two dimensions.

With reference to FIGS. 22B and 22C, the unfolding factor α indicates adegree of unfolding. The unfolding factor may be continuous and may takeany value between 0 and 1.

With reference to FIG. 22B, a high value of α (close to one) results inthe azimuth and inclination angles being reduced by a small amount (whenthose angles are multiplied by a), and the radial coordinate beingincreased by a small amount (when the radial coordinate is increased byan amount proportional to

$\left. {\frac{1}{\alpha} - 1} \right).$

Thus the transformed coordinates in this instance are not dissimilarfrom the coordinates of the points of the model. The points of theunfolded model (at the transformed coordinates) are therefore on anunfolded surface that is similar in form to the closed inner surface ofthe 3-D model. It may be considered that such an unfolded model has asmall degree of unfolding, since the choice of α causes a smalltransformation of the coordinates of the points of the model to pointsof the unfolded model. The resulting unfolded model has a highcurvature.

In contrast, with reference to FIG. 22C, a small value of α (close tozero) results in a large reduction of the azimuthal and inclinationangles (when the angles are multiplied by α) and a large increase in theradial coordinate (when the radial coordinate is increased by an amountproportional to

$\left. {\frac{1}{\alpha} - 1} \right).$

Thus, the transformed coordinates in this instance are distinctlyremoved from the coordinates of the points of the model. The points ofthe unfolded model (at the transformed coordinates) are therefore on anunfolded surface that is not similar in form to the closed inner surfaceof the 3-D model. It may be considered that such an unfolded model has alarge degree of unfolding, since the choice of a causes a largetransformation of the coordinates of the points of the model to pointsof the unfolded model. The resulting unfolded model has a low curvature.

As would be understood by the skilled person, different values of theunfolding factor α result in different “degrees of unfolding”, whereinthe degree of unfolding signifies the curvature of the unfolded model.

At a minimum value of alpha (a maximum degree of unfolding), theunfolded model may have zero curvature. That is to say, the unfoldedmodel may be a flat model that includes the relief details of the 3-Dmodel of the inner surface. Alternatively, a maximum degree of unfoldingmay signify an unfolded surface that has a non-zero curvature. That isto say, as the unfolding factor α tends to zero, the unfoldingtransformation causes a plate Carrée or other cartographic projection ofthe azimuth and inclination coordinates of the model onto a flatsurface, such that the unfolded model becomes a flat model that includesthe relief details of the 3-D model of the surface.

At an intermediate value of α in between the minimum and maximum value,the unfolded model has more curvature than at a maximum degree ofunfolding, but less curvature than a minimum degree of unfolding. It isconsidered that an intermediate value of a, as well as an intermediatedegree of unfolding, correspond to a partially unfolded model.

In some embodiments, the unfolding transformation has the effect oftransforming a notional closed surface centred on the reference point toan open notional surface having zero curvature. In other words, the opennotional surface lies in a plane. In these embodiments, the azimuth andinclination coordinates of each point of the original model aretransformed to respective first and second (x and y) cartesiancoordinates of a corresponding point of the unfolded model in the plane.The transformation may be implemented as a plate carrée transformation(the limiting case of the FIG. 20 transformation as alpha tends tozero), a Mollweide transformation or any other transformation havingdesirable properties for an application at hand. The first and secondcartesian coordinates are thus defined in the plane of the notional opensurface. A third cartesian (z) coordinate is defined as perpendicular tothe plane of the notional open surface. The open notional surface maytherefore be a plane, wherein all points of the plane have the samethird cartesian coordinate.

The radial coordinate of each point of the model is transformed to athird cartesian coordinate of the corresponding point of the unfoldedmodel, wherein the third cartesian coordinate may be defined as the sumof the third cartesian coordinate of the open notional surface, and thenormal distance between the notional closed surface and that point ofthe model.

Alternatively, the cartesian coordinate system may be defined such thatthe notional open surface lies on the first and second cartesiancoordinate axes. In other words, the third cartesian coordinate of eachpoint of the notional open surface is zero. Therefore, the thirdcartesian coordinate of each point of the unfolded model may be definedas the normal distance between the notional closed surface and thecorrespond point of the 3-D model.

In some embodiments, the view of the unfolded model comprisesinformation pertaining to the current state of a time varyinginformation that refers to modeled body part. For example, a view of aheart chamber may include information pertaining to the current state ofa time varying information that refers to that heart chamber. As anexample, the time varying information may be an activation mapsuperimposed on a view of a heart chamber, as described above withreference to FIG. 3. An activation map mapped onto a view of an unfoldedmodel of a heart chamber as shown in FIG. 3, shows a color scaleindicating relative time after an impulse begins that it reaches eachparticular region of the inner surface of the heart chamber.

In one example, the first and/or second view of the unfolded model is apredefined view, wherein the predefined view is displayed in accordancewith at least one of a plurality of predefined viewing parameters, theplurality of predefined viewing parameters comprising: the unfoldingfactor or a value indicative of the degree of unfolding; the valueindicative of the size of notional closed surface; the first and/orsecond surface reference point on the notional closed surface; and theorientation of the first and/or second views of the unfolded surface.

In some embodiments, the first and/or second surface reference pointsmay be determined by a user to define the first and second axesextending from the reference point. Alternatively, the first and axesmay be determined by a user. The user may therefore determine thedirection by which the angular displacement of the points of the modeltakes place, thus determining the direction at which the unfoldingtransformation takes place. In some embodiments, the user may determinethe view of the unfolded model by determining the direction of theangular displacement of the azimuthal and inclination coordinates ofeach point of the model.

A related embodiment of an unfolding transformation takes the model inspherical coordinates as described above (for example transformed from aset of cartesian coordinates) and shrinks the angle coordinates, forexample by multiplication with a positive factor less than unity, suchas a described above. The shrunk angle coordinates are then transformedto 2D Cartesian coordinates using a cartographic projection that dependson radial size (corresponding to the radius of the globe in thecartographic use case), for example one of the following knownprojections: Mollweide, Mercator, Gall stereographic projection,Gall-Peters projection, Eckert IV projection, Ortelius oval, and thelike. The model being transformed will have a characteristic radialsize, for example β described above, such as 30 mm in the case of amodel of the left atrium. To compensate at least in part for theshrinking of the angle coordinates, however, instead of using thischaracteristic radial size for the cartographic projection, an increasedradial size R is used. For example, in some embodiments,

${R = {{\beta + \delta} = \frac{\beta}{\alpha}}},\alpha,\beta$

and δ being as described above. The larger R ensures that the unfoldedmodel is not too small in area. As in the cartographic limiting casedescribed above, the third Cartesian coordinate is taken to be theradial coordinate of each corresponding point of the original sphericalcoordinates.

The transformations described above can be seen to re-distribute reliefdetails on the curved surface so that the surface is divided to anoccupied portion occupied with relief details and a free portion freefrom relief details, as well as increasing the curvature of the curvedsurface. The occupied portion of the increased-curvature curved surfaceis then displayed. The disclosure extends to any display orvisualization method with these steps, whether implemented as describedabove or otherwise. In some embodiments of this method, respectivenotional lines connecting a position of a relief detail before there-distribution to a position of the same relief detail after there-distribution, do not intersect. As described above, the surface maybe non-developable. The surface area of the occupied portion after thecurvature increase may be between half and twice the surface area of theentire surface before the curvature increase, so that surface areas orother features of the relief distribution are preserved to some extent.As in the specific examples described above, the curved surface may be amodel of a surface of a body potion, for example an internal surface ofa body. The body may be an organ of a human or non-human animal, forexample a heart or a portion of a heart as described above. Suchdisplaying or visualization methods may be used in a method of assistinga physician in carrying out a catheterization process, for example asdescribed above. Such an assisting method may comprise receiving datafrom a catheter and generating, based on the data received from thecatheter, a 3-D model of a curved surface of a body part. The generated3-D model comprises relief details distributed across the curved surfaceand the method comprises visualizing or displaying an occupied portionof an increased-curvatures curved surface generated as described aboveand displaying a view of that surface to the physician carrying out thecatheterization process.

There is further provided a method of presenting a three-dimensionalmodel of an surface of heart chamber wall, the method comprising:determining a viewing point and a viewing direction; unfolding the modelso that portions of the surface that are behind a cutting surface goingthrough the vantage point perpendicularly to the viewing direction arepresented peripherally to portions of the surface that are in front thecutting surface; and displaying the unfolded model together with an iconrepresenting the viewing direction.

There is further provided an apparatus for displaying a model using amethod in accordance with some methods, the apparatus comprising a userinterface configured to allow a user to indicate a desired vantage pointand a desired viewing direction.

In some embodiments, the apparatus further comprises a display showingthe orientation of the viewing direction near the resulting unfoldedthree-dimensional model.

In some embodiments, the user interface allows the user to indicatedifferent vantage points and/or viewing angle continuously, and thedisplay shows the unfolded model changing simultaneously with thevantage point and/or viewing angle.

With reference to FIG. 23, a display 8 displays a first view of anunfolded model of a heart chamber on the left hand side, and a secondview of the unfolded model on the right hand side, with a differentorientation to the first view. In the first view, the followinganatomical features are clearly shown: superior right pulmonary vein(PV) 10; inferior right PV 12, anomalous extra right PV 14, inferiorleft PV 16, superior left PV 18, and left atrium appendage 20. Some ofthe same features are also shown clearly in the second view, forexample, superior right PV (SRPV) 10, inferior right PV (IRPV) 12,anomalous extra right PV 14, and inferior left PV (ILPV) 16. The firstand second views described with reference to FIG. 23 also showrespective images 32 and 34, which are views of the unfolded model whenonly partially unfolded. These partially unfolded views can be used asadditional orientation aids, as they aid the user in understanding theorientation of the fully unfolded view (a view of the unfolded model ata maximum degree of unfolding). The orientation may also be facilitatedby a continuous move between the close and open (original model andunfolded) views, so that features in one view are shown to become thecorresponding features on the other view. A view of the original modelof the surface of the heart chamber and/or a partly unfolded view may bedisplayed together with a view of the fully unfolded model.

The orientation of the second view is at a 90° angle to the orientationof the first model. However, the orientation may be at a 180° angle tothe orientation of the first model. Optionally, the orientation of thesecond view may be at any angle with respect to the first view.

In advantageous embodiments, the orientation of the second view of themodel is at an angle greater than 0° and less than 180° to theorientation of the first view. Optionally, this angle is between 60° and120°, and preferably 90°. That is to say, in advantageous embodiments,the first and second views of the unfolded model may be perpendicular toone another.

With reference to FIG. 23, the first and second view of the unfoldedmodel may each further comprise an indication for the position of acatheter 22 inside the body. The position of the catheter may changeinside the body (if the body is a heart chamber, the catheter may moveinside the heart chamber) and it may be difficult to visualise themovement of the catheter in one view of the unfolded model. This may bethe case particularly if the catheter is moving in a direction thatappears to be perpendicular to the plane of a screen displaying the view(i.e. the catheter appears to be moving towards or away from the planeof the screen). Therefore, a user viewing the unfolded model may not beable to identify the exact position of the catheter when viewing onlyone view of the unfolded model displayed at one orientation.

A second view of the unfolded model at a perpendicular orientation tothe first view will be able to display the catheter movement as amovement along the plane of the screen, thus clearly displaying to auser the position of the catheter within the body. It is thereforeadvantageous to provide two perpendicular views of the unfolded model atthe same time, such that a user can always determine the position of thecatheter and the direction in which it is moving inside the body.

Again with reference to FIG. 23, first view of the unfolded model isaccompanied by an icon 30 that shows the viewing direction. The secondview may optionally include the icon as well as or instead of the firstview. For example, the icon may have the shape of a hat-wearing head.When the viewing direction changes, the icon keeps looking at theviewing direction, and thus the orientation of the icon changes. Theicon may thus be indicative of the direction from which the unfoldedmodel is viewed. If the body is an internal organ (or a portion thereof)of an animal or human, the icon may be indicative of the direction atwhich the model is viewed with respect to the animal or human. The iconmay have any other form that may easily convey its orientation, e.g., awhole person statuette.

In some embodiments of the invention, the model is provided in arbitrarycoordinates, which may be, for example, Cartesian. As a first step, thearbitrary coordinates are transferred to default Cartesian coordinateswhere the origin is at a default position, and the various axes facedefault directions. For example, the origin may be by default at thecenter of the largest sphere contained in the model, with one axisfacing the back of the patient (who's heart chamber is modelled), andanother axis facing the head of the patient. The default Cartesiancoordinates determine a default unfolding, e.g., the default coordinatesare conventionally transformed to spherical coordinates, and these areused in the unfolding, e.g., using a cartographic projection for theangular coordinates. This default determines a default surface (goingthrough the origin and perpendicularly to the default viewing direction,i.e., in parallel to the patient's back) that cuts the heart chamber.The unfolding brings parts of the heart chamber wall that are behind thecutting surface to the front of the cutting surface, but at largerviewing angles, that is, at the periphery of the unfolded model. Inother words, wall portions in front of the cutting surface are at thecenter of the unfolded model, while wall portions behind the cuttingsurface are at the periphery of the unfolded model.

In some embodiments, the physician may change the position of theCartesian coordinate system, that is, move the origin. Moving the originmay be useful, for example, for bringing an area of interest to themiddle of the wall portion in front of the cutting surface, withoutchanging the viewing direction. Furthermore, the physician may changethe viewing direction (perpendicularly to which the cutting surfacelies). This way, the cutting surface is perpendicular to the viewingdirection but not parallel to the patient's back. The physician mycontrol both azimuthal and inclination angles of the viewing direction,optionally, separately. FIGS. 24A to 24E illustrate a view of anunfolded model of a heart chamber at five different degrees ofunfolding, represented by an unfolding parameter from 2% to 100%, asindicated in the figures. In other words, the figures show a progressiveunfolding of a model of a heart chamber to an unfolded model. Theunfolding parameter shown in these figures is indicative of theunfolding factor α described above. For example, an unfolding parameterof 100% illustrated in FIG. 24E represents a maximum degree of unfoldingand hence unfolding factor α=0 equivalent to a flat cartographicprojection. Similarly, an unfolding parameter of 2% as shown in FIG. 24Arepresents a small degree of unfolding and a value of α close to 1.

The 3-D model of the surface of the body may be of any other 3-D bodythat models the surface of the body or any digital representation ofsuch a 3-D body. The 3-D model of the surface of the heart chamber maybe any 3-D body that models the surface of the heart chamber or anydigital representation of such a 3-D body. It is noted that a heartchamber typically includes a blood pool defined by a wall. The walltypically has openings for connecting to blood vessels. Further, thewall is not necessarily smooth and/or of constant depth, rather, it mayinclude relief details and regions of various thicknesses. The walldefines the blood pool volume. In some embodiments, the 3-D model of theheart chamber models the blood pool and the wall surface that definesthe blood pool. In some embodiments, the 3-D model is defined by pointson a model surface modelling the surface. That is to say, in someembodiments, the model surface is a model of the wall surface thatdefines the blood pool of the heart chamber. In some embodiments, the3-D model also models the blood vessels entering the heart chamber, orat least portions thereof. The thickness of the model wall at any pointis not necessarily indicative of the wall thickness of the heart chamberat the same point. In some embodiments, the 3-D model models the surfaceof the heart chamber wall as viewed from within the heart chamber. Insome embodiments, the volume surrounded by the model surface withinwhich the reference point is defined is the blood pool of the heartchamber.

General

As used herein with reference to quantity or value, the term “about”means “within ±10% of”.

The terms “comprises”, “comprising”, “includes”, “including”, “having”and their conjugates mean: “including but not limited to”.

The term “consisting of” means: “including and limited to”.

The term “consisting essentially of” means that the composition, methodor structure may include additional ingredients, steps and/or parts, butonly if the additional ingredients, steps and/or parts do not materiallyalter the basic and novel characteristics of the claimed composition,method or structure.

As used herein, the singular form “a”, “an” and “the” include pluralreferences unless the context clearly dictates otherwise. For example,the term “a compound” or “at least one compound” may include a pluralityof compounds, including mixtures thereof.

The words “example” and “exemplary” are used herein to mean “serving asan example, instance or illustration”. Any embodiment described as an“example” or “exemplary” is not necessarily to be construed as preferredor advantageous over other embodiments and/or to exclude theincorporation of features from other embodiments.

The word “optionally” is used herein to mean “is provided in someembodiments and not provided in other embodiments”. Any particularembodiment may include a plurality of “optional” features except insofaras such features conflict.

As used herein the term “method” refers to manners, means, techniquesand procedures for accomplishing a given task including, but not limitedto, those manners, means, techniques and procedures either known to, orreadily developed from known manners, means, techniques and proceduresby practitioners of the chemical, pharmacological, biological,biochemical and medical arts.

As used herein, the term “treating” includes abrogating, substantiallyinhibiting, slowing or reversing the progression of a condition,substantially ameliorating clinical or aesthetical symptoms of acondition or substantially preventing the appearance of clinical oraesthetical symptoms of a condition.

Throughout this application, embodiments may be presented with referenceto a range format. It should be understood that the description in rangeformat is merely for convenience and brevity and should not be construedas an inflexible limitation on the scope of the present disclosure.Accordingly, the description of a range should be considered to havespecifically disclosed all the possible subranges as well as individualnumerical values within that range. For example, description of a rangesuch as “from 1 to 6” should be considered to have specificallydisclosed subranges such as “from 1 to 3”, “from 1 to 4”, “from 1 to 5”,“from 2 to 4”, “from 2 to 6”, “from 3 to 6”, etc.; as well as individualnumbers within that range, for example, 1, 2, 3, 4, 5, is and 6. Thisapplies regardless of the breadth of the range.

Whenever a numerical range is indicated herein (for example “10-15”, “10to 15”, or any pair of numbers linked by these another such rangeindication), it is meant to include any number (fractional or integral)within the indicated range limits, including the range limits, unlessthe context clearly dictates otherwise. The phrases“range/ranging/ranges between” a first indicate number and a secondindicate number and “range/ranging/ranges from” a first indicate number“to”, “up to”, “until” or “through” (or another such range-indicatingterm) a second indicate number are used herein interchangeably and aremeant to include the first and second indicated numbers and all thefractional and integral numbers therebetween.

Although the present disclosure has been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications and variations that fall within the spirit and broad scopeof the appended claims.

It is the intent of the Applicant(s) that all publications, patents andpatent applications referred to in this specification are to beincorporated in their entirety by reference into the specification, asif each individual publication, patent or patent application wasspecifically and individually noted when referenced that it is to beincorporated herein by reference. In addition, citation oridentification of any reference in this application shall not beconstrued as an admission that such reference is available as prior artto the present invention. To the extent that section headings are used,they should not be construed as necessarily limiting. In addition, anypriority document(s) of this application is/are hereby incorporatedherein by reference in its/their entirety.

It is appreciated that certain features of the present disclosure, whichare, for clarity, described in the context of separate embodiments, mayalso be provided in combination in a single embodiment. Conversely,various features of the present disclosure, which are, for brevity,described in the context of a single embodiment, may also be providedseparately or in any suitable subcombination or as suitable in any otherdescribed embodiment of the present disclosure. Certain featuresdescribed in the context of various embodiments are not to be consideredessential features of those embodiments, unless the embodiment isinoperative without those elements.

What is claimed is:
 1. An apparatus comprising: an input configured toreceive signals from a catheter, wherein the signals are indicative ofmeasurements taken by the catheter inside a heart chamber; a processorconfigured to: (a) convert the signals into coordinates of pointsdefining a model surface modelling a three-dimensional surface of theheart chamber; and (b) apply a transformation to the points of the modelto transform each of the points to a corresponding point of an unfoldedmodel; and a display for displaying a view of the unfolded model,wherein the transformation has the effect of transforming a notionalclosed surface centred on a reference point within a volume surroundedby the model surface to a notional open surface such that for each pointof the model, a normal distance between the notional closed surface andthe point is substantially equal to a normal distance between thenotional open surface and the corresponding point of the unfolded model.2. The apparatus of claim 1, further comprising a user interfaceconfigured to receive display instructions from a user, wherein theapparatus is configured to display a view of the unfolded model inaccordance with the display instructions.
 3. The apparatus of claim 1,wherein the measurements taken inside the heart chamber includeelectrical measurements.
 4. The apparatus of claim 1, wherein themeasurements taken inside the heart chamber include magneticmeasurements.
 5. The apparatus of claim 1, wherein the view of theunfolded model shows at least 80% of the points of the unfolded model.6. The apparatus of claim 1, wherein the view of the unfolded modelshows all of the points of the unfolded model.
 7. The apparatus of claim1, wherein the apparatus is configured to display an icon indicative thedirection at which the unfolded model is viewed with respect to a humanbody.
 8. The apparatus of claim 2, wherein the display instructionscomprise the orientation of the view of the unfolded model.
 9. Theapparatus of claim 1, wherein the apparatus is configured to display asecond view of the unfolded model.
 10. The apparatus of claim 9, whereinthe second view has a viewing direction that is opposite of the viewingdirection of the first view.
 11. The apparatus of claim 9, wherein thesecond view has a viewing direction that is perpendicular to the viewingdirection of the first view.
 12. The apparatus of claim 9, wherein thesecond view is displayed for an overlapping time period together withthe first view.
 13. The apparatus of claim 9, wherein the first andsecond views are displayed during non-overlapping respective timeperiods.
 14. The apparatus of claim 2, wherein the apparatus isconfigured to display a second view of the unfolded model and thedisplay instructions comprises the orientation of the second view of theunfolded model.
 15. The apparatus of claim 1, wherein the apparatus isconfigured to display information pertaining to time varying informationthat refers to the heart chamber.
 16. The apparatus of claim 15, whereinthe time varying information is an electrical activation map.
 17. Theapparatus of claim 15, wherein the time varying information is an edemamap.
 18. The apparatus of claim 1, wherein the apparatus is configuredto simultaneously display a plurality of views of the unfolded model ata plurality of different orientations.
 19. The apparatus of claim 1,wherein the apparatus is configured to sequentially display a pluralityof views of the unfolded model at respective different orientations. 20.The apparatus of claim 1, wherein the apparatus is configured tosimultaneously display a plurality of views of the unfolded model,wherein each view is indicative of a different degree of unfolding. 21.The apparatus of claim 1, wherein the converting comprises an unfoldingtransformation comprising reducing azimuth and inclination angles, ofeach point of the model, about a reference point and increasing theradial distance between each point of the model and the reference point.22. The apparatus of claim 21, wherein the unfolding transformationreduces the azimuth and inclination angles and increases the radialdistance such that a length between two points of the model is preservedfollowing the unfolding transformation.
 23. The apparatus of claim 21,comprising a user interface, configured to allow a user to control adegree of the unfolding.
 24. The apparatus of claim 21, comprising aninterface configured to allow a user to determine the reference point.25. The apparatus of claim 1, wherein the processor is configured to:convert the signals into coordinates of points defining a model surfacemodelling the three-dimensional surface of the heart chamber, and intocoordinates for the position of the catheter within the heart chamber;and provide for display the unfolded model together with an iconrepresenting the catheter at the said position in the unfolded model.26. An apparatus for displaying a model the apparatus comprising a userinterface configured to allow a user to indicate a desired vantage pointand a desired viewing direction, and a processor configured to unfoldthe model so that portions of the surface that are behind a cuttingsurface are presented peripherally to portions of the surface that arein front the cutting surface, where the cutting surface is defined asgoing through the indicated viewing point perpendicularly to theindicated viewing direction; and provide the unfolded model for displaytogether with an icon representing the viewing direction, wherein themodel includes a model of a catheter at a position inside the heartchamber, and the processor is configured to provide for display theunfolded model together with an icon representing the catheter at thesaid position in the unfolded model.
 27. The apparatus of claim 26,further comprising a display showing the orientation of the viewingdirection near the resulting unfolded three-dimensional model.
 28. Theapparatus of claim 26, wherein the user interface allows the user toindicate different vantage points and/or viewing angle continuously, andthe display shows the unfolded model changing simultaneously with thevantage point and/or viewing angle.
 29. The apparatus of claim 26,wherein the unfolding uses a transformation that has the effect oftransforming a notional closed surface centred on a reference pointwithin a volume surrounded by the model surface to a notional opensurface such that for each point of the model, a normal distance betweenthe notional closed surface and the point is substantially equal to anormal distance between the notional open surface and the correspondingpoint of the unfolded model.